Duplicate declaration of br-ex in tripleo_network_config

Summary:
We see to be declaring br-ex twice in the multiple_nics.j2 template:
https://github.com/openstack/tripleo-ansible/blob/master/tripleo_ansible/roles/tripleo_network_config/templates/multiple_nics/multiple_nics_dvr.j2#L24-L26

And obviously after the tenant network is configured, we configure br-ex:
https://github.com/openstack/tripleo-ansible/blob/master/tripleo_ansible/roles/tripleo_network_config/templates/multiple_nics/multiple_nics_dvr.j2#L43-L44

But the second name: section under the tenant network seems to be breaking the deployment. See the details below

Environment:
[root@tripleo-director overcloud]# rpm -qa | grep tripleo-ansible
tripleo-ansible-2.1.0-0.20201102184033.62a7fa9.el8.noarch

Details:
This part of the network config:
https://github.com/openstack/tripleo-ansible/blob/master/tripleo_ansible/roles/tripleo_network_config/templates/multiple_nics/multiple_nics_dvr.j2#L24-L26

Results in two br-NAME bridges in OvS:
```
- type: ovs_bridge
  name: br-tenant
  name: br-ex
  mtu: 9000
  dns_servers: ['8.8.8.8']
  use_dhcp: false
  addresses:
  - ip_netmask:
      172.16.0.120/24
  routes: []
  members:
  - type: interface
    name: nic5
    mtu: 9000
    use_dhcp: false
    primary: true
- type: ovs_bridge
  name: br-ex
  mtu: 9000
  dns_servers: ['8.8.8.8']
  use_dhcp: false
  addresses:
  - ip_netmask:
      172.20.10.23/16
  routes: [{'default': True, 'next_hop': '172.20.0.254'}]
```

This doesn't create the br-tenant bridge, and the deployment fails. We can see the bridge missing in OvS:
```
[root@overcloud-controller-0 ~]# ovs-vsctl show
e970fec3-95a4-48e2-abcf-06b018392c52
    Bridge br-ex
        fail_mode: standalone
        Port enp6s0
            Interface enp6s0
        Port br-ex
            Interface br-ex
                type: internal
    ovs_version: "2.13.0"
```

If I remove the unnecessary br-ex declaration, it all works as expected:
```
- type: ovs_bridge
  name: br-tenant
  mtu: 9000
  dns_servers: ['8.8.8.8']
  use_dhcp: false
  addresses:
  - ip_netmask:
      172.16.0.120/24
  routes: []
  members:
  - type: interface
    name: nic5
    mtu: 9000
    use_dhcp: false
    primary: true
- type: ovs_bridge
  name: br-ex
  mtu: 9000
  dns_servers: ['8.8.8.8']
  use_dhcp: false
  addresses:
  - ip_netmask:
      172.20.10.23/16
  routes: [{'default': True, 'next_hop': '172.20.0.254'}]
```

Re-run os-net-config:
```
[root@overcloud-controller-0 ~]# os-net-config -c /etc/os-net-config/config.yaml -vvv
[2020/11/26 01:02:20 AM] [INFO] Using config file at: /etc/os-net-config/config.yaml
[2020/11/26 01:02:20 AM] [INFO] Ifcfg net config provider created.
[2020/11/26 01:02:20 AM] [INFO] Not using any mapping file.
[2020/11/26 01:02:21 AM] [INFO] Finding active nics
[2020/11/26 01:02:21 AM] [INFO] enp3s0 is an active nic
[2020/11/26 01:02:21 AM] [INFO] enp6s0 is an active nic
[2020/11/26 01:02:21 AM] [INFO] enp2s0 is an active nic
[2020/11/26 01:02:21 AM] [INFO] enp5s0 is an active nic
[2020/11/26 01:02:21 AM] [INFO] lo is not an active nic
[2020/11/26 01:02:21 AM] [INFO] enp1s0 is an active nic
[2020/11/26 01:02:21 AM] [INFO] enp4s0 is an active nic
[2020/11/26 01:02:21 AM] [INFO] ovs-system is not an active nic
[2020/11/26 01:02:21 AM] [INFO] br-ex is not an active nic
[2020/11/26 01:02:21 AM] [INFO] No DPDK mapping available in path (/var/lib/os-net-config/dpdk_mapping.yaml)
[2020/11/26 01:02:21 AM] [INFO] Active nics are ['enp1s0', 'enp2s0', 'enp3s0', 'enp4s0', 'enp5s0', 'enp6s0']
[2020/11/26 01:02:21 AM] [INFO] nic6 mapped to: enp6s0
[2020/11/26 01:02:21 AM] [INFO] nic1 mapped to: enp1s0
[2020/11/26 01:02:21 AM] [INFO] nic5 mapped to: enp5s0
[2020/11/26 01:02:21 AM] [INFO] nic2 mapped to: enp2s0
[2020/11/26 01:02:21 AM] [INFO] nic4 mapped to: enp4s0
[2020/11/26 01:02:21 AM] [INFO] nic3 mapped to: enp3s0
[2020/11/26 01:02:21 AM] [INFO] adding interface: enp1s0
[2020/11/26 01:02:21 AM] [INFO] adding interface: enp2s0
[2020/11/26 01:02:21 AM] [INFO] adding interface: enp3s0
[2020/11/26 01:02:21 AM] [INFO] adding interface: enp4s0
[2020/11/26 01:02:21 AM] [INFO] adding bridge: br-tenant
[2020/11/26 01:02:21 AM] [INFO] adding interface: enp5s0
[2020/11/26 01:02:21 AM] [INFO] adding bridge: br-ex
[2020/11/26 01:02:21 AM] [INFO] adding custom route for interface: br-ex
[2020/11/26 01:02:21 AM] [INFO] adding interface: enp6s0
[2020/11/26 01:02:21 AM] [INFO] applying network configs...
[2020/11/26 01:02:21 AM] [INFO] No changes required for interface: enp1s0
[2020/11/26 01:02:21 AM] [INFO] No changes required for interface: enp2s0
[2020/11/26 01:02:21 AM] [INFO] No changes required for interface: enp3s0
[2020/11/26 01:02:21 AM] [INFO] No changes required for interface: enp4s0
[2020/11/26 01:02:21 AM] [INFO] No changes required for interface: enp6s0
[2020/11/26 01:02:21 AM] [INFO] No changes required for bridge: br-ex
[2020/11/26 01:02:21 AM] [INFO] running ifdown on interface: enp5s0
[2020/11/26 01:02:21 AM] [INFO] running ifdown on bridge: br-tenant
[2020/11/26 01:02:21 AM] [INFO] Writing config /etc/sysconfig/network-scripts/ifcfg-enp5s0
[2020/11/26 01:02:21 AM] [INFO] Writing config /etc/sysconfig/network-scripts/ifcfg-br-tenant
[2020/11/26 01:02:21 AM] [INFO] running ifup on bridge: br-tenant
[2020/11/26 01:02:25 AM] [INFO] running ifup on interface: enp5s0
```

And we can now see the bridges and IP that was previously missing:
```
[root@overcloud-controller-0 ~]# ovs-vsctl show
e970fec3-95a4-48e2-abcf-06b018392c52
    Bridge br-tenant
        fail_mode: standalone
        Port enp5s0
            Interface enp5s0
        Port br-tenant
            Interface br-tenant
                type: internal
    Bridge br-ex
        fail_mode: standalone
        Port enp6s0
            Interface enp6s0
        Port br-ex
            Interface br-ex
                type: internal
    ovs_version: "2.13.0"
[root@overcloud-controller-0 ~]# ip -o a
1: lo inet 127.0.0.1/8 scope host lo\ valid_lft forever preferred_lft forever
1: lo inet6 ::1/128 scope host \ valid_lft forever preferred_lft forever
2: enp1s0 inet 192.168.24.16/24 brd 192.168.24.255 scope global enp1s0\ valid_lft forever preferred_lft forever
2: enp1s0 inet6 fe80::546f:14ff:fef3:7/64 scope link \ valid_lft forever preferred_lft forever
3: enp2s0 inet 172.16.1.179/24 scope global enp2s0\ valid_lft forever preferred_lft forever
3: enp2s0 inet6 fe80::546f:14ff:fef3:8/64 scope link \ valid_lft forever preferred_lft forever
4: enp3s0 inet 172.16.3.202/24 scope global enp3s0\ valid_lft forever preferred_lft forever
4: enp3s0 inet6 fe80::546f:14ff:fef3:9/64 scope link \ valid_lft forever preferred_lft forever
5: enp4s0 inet 172.16.2.6/24 scope global enp4s0\ valid_lft forever preferred_lft forever
5: enp4s0 inet6 fe80::546f:14ff:fef3:a/64 scope link \ valid_lft forever preferred_lft forever
6: enp5s0 inet6 fe80::546f:14ff:fef3:b/64 scope link \ valid_lft forever preferred_lft forever
7: enp6s0 inet6 fe80::546f:14ff:fef3:c/64 scope link \ valid_lft forever preferred_lft forever
11: br-ex inet 172.20.10.23/16 brd 172.20.255.255 scope global br-ex\ valid_lft forever preferred_lft forever
11: br-ex inet6 fe80::546f:14ff:fef3:c/64 scope link \ valid_lft forever preferred_lft forever
12: br-tenant inet 172.16.0.120/24 brd 172.16.0.255 scope global br-tenant\ valid_lft forever preferred_lft forever
12: br-tenant inet6 fe80::546f:14ff:fef3:b/64 scope link \ valid_lft forever preferred_lft forever
```

Steps to reproduce:
1. Follow the guide for deploying with network isolation:
https://docs.openstack.org/project-deploy-guide/tripleo-docs/latest/features/network_isolation.html
2. Run the deployment. It fails for me with this error:
```
2020-11-26 10:44:06,395 p=700865 u=stack n=ansible | 2020-11-26 10:44:06.394124 | 566f14f3-0016-a095-f7d9-000000000be2 | FATAL | Check Controllers availability | overcloud-controller-0 | item=172.16.0.120 | error={"ansible_loop_var": "controller", "changed": false, "cmd": ["ping", "-w", "10", "-c", "1", "172.16.0.120"], "controller": "172.16.0.120", "delta": "0:00:10.007624", "end": "2020-11-26 00:44:06.340714", "msg": "non-zero return code", "rc": 1, "start": "2020-11-26 00:43:56.333090", "stderr": "", "stderr_lines": [], "stdout": "PING 172.16.0.120 (172.16.0.120) 56(84) bytes of data.\n\n--- 172.16.0.120 ping statistics ---\n10 packets transmitted, 0 received, 100% packet loss, time 218ms", "stdout_lines": ["PING 172.16.0.120 (172.16.0.120) 56(84) bytes of data.", "", "--- 172.16.0.120 ping statistics ---", "10 packets transmitted, 0 received, 100% packet loss, time 218ms"]}
```

The details section explains the reason for this.