neutron: l3-agent stop causes failover of router

Stopping L3 agent shouldn't automatically cause failover of router. If keepalived process or router is working it can still keep active router on control01 node even if L3 agent is stopped there.

By VIP address do You mean this IP address which is managed by keepalived and moved between ha interfaces on router? Are all other IPs, like like attached subnets' interfaces, external gateway, etc. configured on control02 after this?
And please also tell us what is router's status in Neutron's API. Is it master on both control01 and control02?

Also can You attach some logs from keepalived, keepalived-state-change-monitor and l3 agent from both nodes (control01 and control02)?

Stopping L3 agent through ``docker stop``, keepalived process run in L3 Agent container, container exited and keepalived will be killed.

VIP is external gateway ip.

If You stopped L3 agent and keepalived process together, than keepalived from other node will decide to be new master and L3 agent on this other node will configure everything for router. That is how failover works.
But in such case there is nothing what could do cleaning of router's config on "old" node (control01 in Your case) as You just stopped L3 agent there. So IMO this is not an neutron issue as neutron works here as expected.
Maybe Kolla shouldn't run keepalived processes for routers in same container as L3 agent?

We could adopt TripleO approach to spawn those processes in separate containers - then neutron-l3-agent stop would not affect those services.

https://review.opendev.org/#/c/566559/1