neutron-dynamic-routing announces routes for disabled routers

[Felix Huettner]

neutron routers can be disabled, thereby basically removing them from their l3 agents.
They will no longer accept, process or forward packets once they are disabled.

Currently if a router is set to disabled the dragents still advertise the routes to its networks and floating ips.
Even though the router is actually not active and can not handle these packets.
This causes the upstream routers to still know these routes and try to forward packets to this disabled router.

For example for internet network this causes unneeded traffic on the upstream routers and the network nodes.
They will receive traffic that they forward to the network node which then will drop this traffic as the router is gone.

It would be ideal if routes for disabled routers are no longer advertised by the dragents.
This would cause upstream routers to loose the routes to these network/fips and allow them to drop the traffic as early as possible.

[Felix Huettner (felix.huettner)]

Fix at https://review.opendev.org/c/openstack/neutron-dynamic-routing/+/882560