Add more info to ShardStats JXM bean

Add more info to ShardStats JXM bean

Added more raft state information to the ShardStats, including lastIndex,
lastTerm, snapShotIndex, snapshotTerm, replicatedToAllIndex, info about
each follower (if the leader), and peer addresses. Basically all the
pertinent raft actor state is now reported.

Instead of having the Shard update the stats bean as things change,
which would be difficult with some of the state, I changed ShardStats to
send a GetOnDemandRaftState message to the shard actor which returns all
the state info in an OnDemandRaftState reply. This captures the state in
a thread-safe manner. Since each piece of information is returned by the
ShardStats bean in separate methods, I didn't want each call to send the
message so I cache the last OnDemandRaftState reply for 2 seconds.

With this change, the Shard no longer needs to keep the ShardStats up to date
with the current state.

Change-Id: I1775ba35747c68028f5c3e31789b958d35afa172
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>