BUG 2185: Expand the scope of sync status to cover a slow follower

BUG 2185: Expand the scope of sync status to cover a slow follower

Previously sync status was used only in the startup scenario
to make the controller appear to the external world as not
synced up unless it had received atleast data till the commitIndex
which the leader reported when it sent the follower it's first
heartbeat.

Now we also track when a new update is sent from the Leader to the
Follower and if the Follower is behind the Leader by a threshold
(hardcoded for now) then we consider the Follower as out-of-sync

Also I added the member name in the ShardManager bean so that is another
place from which we can figure out on which node we are running.

Change-Id: I1ba02575a0a1ac5d601af559f41971f2f5736f9d
Signed-off-by: Moiz Raja <moraja@cisco.com>