Comment 15 for bug 1931696

The patch of https://review.opendev.org/c/openstack/neutron/+/666991 which introduced the config option ``explicitly_egress_direct=True/False`` had fixed the following problems:
1. the egress flooding issue on br-int when enable openvswitch(openflow) security group driver
https://bugs.launchpad.net/neutron/+bug/1732067

2. fix the east-west traffic broken of dvr
https://bugs.launchpad.net/neutron/+bug/1831534 (this bug is for VLAN network, but the issue is not vlan only).

3. fix some potential ingress flood issue on br-int

And I had put some issues here as well:
https://bugs.launchpad.net/neutron/+bug/1934666/comments/5

So, not use explicitly_egress_direct=True, you have to face these issues.

Another thing is that as I said in the release note before, do not use ``explicitly_egress_direct=True`` in host which enable dvr_snat and compute service. There are too many cases need to cover, please try to combine the following cases for DVR:
1. vlan/vxlan
2. dvr/dvr+ha
3. agent mode(dvr, dvr_snat, dvr_no_external)
4. east-west traffic and north-south traffic with the Scenario of src and dest in or not in same host
5. IPv6
6. allowed_address_pair
7. enable/disabl openflow firewall
8. HA router failover
The final cases is too many to cover.

And FYI, we had mark that dvr_snat + compute services is not supported.
https://review.opendev.org/c/openstack/neutron/+/801503