The L3 agent gets keepalived state change notifications via
a unix domain socket. These events are now batched and
send out as a single RPC to the server. In case the same
router got updated multiple times during the batch period,
only the latest state is sent.
Partially-Implements: blueprint report-ha-router-master
Change-Id: I36834ad3d9e8a49a702f01acc29c7c38f2d48833