[Neutron][L3 HA] After destroying controller with active ha_state all agents are standby

Environment:
MOS 8.0
3 controllers + 2 computes + VLAN L3 HA or VxLAN L2 POP L3 HA

Steps to reproduce:
1. Create network1, network2
2. Create router1 and connect it with network1, network2 and external net
3. Boot vm1 in network1
4. Boot vm2 in network2 and associate floating ip
5. Add rules for ping
6. Find node with active ha_state for router
7. If node from step 6 isn't primary controller, reschedule router1 to primary by banning all another and then clear them
8. Start ping vm2 from vm1 by floating ip
9. Destroy primary controller (l3 agent on it should be with ACTIVE ha_state)
10. Stop ping

Expected results:
ping lost no more than 10 packets
another l3-agent became active

Actual result:
ping lost no more than 10 packets
but all l3-agents are standby

root@node-4:~# neutron l3-agent-list-hosting-router fb6a7255-9b5c-46f5-a883-28426ebc99d8
+--------------------------------------+--------------------------+----------------+-------+----------+
| id | host | admin_state_up | alive | ha_state |
+--------------------------------------+--------------------------+----------------+-------+----------+
| 759a3b60-645b-46df-bc05-43cefe8f4760 | node-5.test.domain.local | True | :-) | standby |
| b66c0707-1ab6-4e75-ad94-eab6f1134769 | node-3.test.domain.local | True | xxx | standby |
| 30e36618-dcae-44d9-89e8-1ce78c23be3f | node-4.test.domain.local | True | :-) | standby |
+--------------------------------------+--------------------------+----------------+-------+----------+

This problem also exist for non primary controller with l3 agent with ACTIVE ha_state.