public class SyncStatusTracker
extends Object
The SyncStatusTracker tracks if a Follower is in sync with any given Leader or not
 When an update is received from the Leader and the update happens to be the first update
 from that Leader then the SyncStatusTracker will not mark the Follower as not in-sync till the
 Followers commitIndex matches the commitIndex that the Leader sent in it's very first update.
 Subsequently when an update is received the tracker will consider the Follower to be out of
 sync if it is behind by 'syncThreshold' commits.