As described in the bug, when a HA router transitions from "master" to
"backup", "keepalived" processes will set the virtual IP in all other
HA routers. Each HA router will then advert it and "keepalived" will
decide, according to a trivial algorithm (higher interface IP), which
one should be "master". At this point, the other "keepalived" processes
running in the other servers, will remove the HA router virtual IP
assigned an instant before
To avoid transitioning some routers form "backup" to "master" and then
to "backup" in a very short period, this patch delays the "backup" to
"master" transition, waiting for a possible new "backup" state. If
during the waiting period (set to the HA VRRP advert time, 2 seconds
default) to set the HA state to "master", the L3 agent receives a new
"backup" HA state, the L3 agent does nothing.
Closes-Bug: #1837635
Change-Id: I70037da9cdd0f8448e0af8dd96b4e3f5de5728ad
3f022a193f