[Neutron][L3 HA] After ban l3 agent with active ha_state for router active ha_state is not rescheduled

[Georgy Dyuldin]

After ban active l3 agent all other alive agents still were standby:
root@node-2:~# neutron l3-agent-list-hosting-router router04
+--------------------------------------+--------------------------+----------------+-------+----------+
| id | host | admin_state_up | alive | ha_state |
+--------------------------------------+--------------------------+----------------+-------+----------+
| c892d830-1c24-410b-acb7-9529074ca510 | node-2.test.domain.local | True | xxx | active |
| 872b8226-a6ee-4251-9433-5729c96cd6ff | node-1.test.domain.local | True | :-) | standby |
| 934bae58-6863-4d77-94c9-d6422516c504 | node-5.test.domain.local | True | :-) | standby |
+--------------------------------------+--------------------------+----------------+-------+----------+

/var/lib/neutron/ha_confs/<router_id>/state shows backup for all alive agents

Steps:
1) Create security group with allowing ICMP traffic
2) Create net, subnet
3) Create router, set gateway and interface to created network
4) Boot VM in net and associate floating IP
5) Check ping to VM's Floating IP
6) Ban l3 agent with ha_state=active
7) Wait until another alive agent will be active
8) Check ping to VM's Floating IP
Expected result: after banning another alive agent should be active
Current result: all other alive agents are standby

Description of the environment:
 - MOS 10.0 #1505
 - 3 conrtollers, 2 computes, 1 cinder
 - Neutron VLAN with L3 HA

[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: 10.0/newton
Change author: Sergey Belous <email address hidden>
Review: https://review.fuel-infra.org/32539

[Ann Taraday (akamyshnikova)]

Neutron code is missing netns_cleanup script improvements https://review.fuel-infra.org/#/c/18773/.