If l3-agent was restarted by a regular action, such as config change,
package upgrade, manually service restart etc. We should not set the
HA port down during such scenarios. Unless the physical host was
rebooted, aka the VRRP processes were all terminated.
This patch adds a new RPC call during l3 agent init, it will try to
retrieve the HA router count first. And then compare the VRRP process
(keepalived) count and 'neutron-keepalived-state-change' count
with the hosting router count. If the count matches, then that
set HA port to 'DOWN' state action will not be triggered anymore.
Closes-Bug: #1798475
Change-Id: I5e2bb64df0aaab11a640a798963372c8d91a06a8