Comment 14 for bug 1843557

So without dvr-snat on neutron-openvswitch-octavia (comment #7):

1) l3 agents are installed on octavia units;

2) qrouter and fip namespaces are attempted to be created and fail to do so if octavia is deployed into LXD (nested namespaces);

3) snat namespaces are not created on neutron-openvswitch-octavia units (they are scheduled only to dvr_snat agents);

3) radvd is set up only in qrouter namespaces, not snat namespaces;

4) o-hm0 interfaces are unable to obtain IPv6 addresses while amphorae can because they reside on computes where qrouter namespaces are successfully created.

In essence:

* we need to use centralized routers (l3ha or not) for the management network only in `configure-resources` action in octavia to make IPv6 SLAAC setup work;
  * openstack router create --centralized --ha # ...
* l3 agents do not need to be installed on neutron-openvswitch-octavia.