BUG 2817 : Handle ServerRemoved message in Shard/ShardManager
When a server is removed and the new ServerConfiguration is
replicated and consensus has been reached on it the RaftActor
sends a ServerReoved message to the Replica which has just been
removed.
This ServerRemoved messsage is received by the Shard and it
forwards the message to the ShardManager. The ShardManager
then removes the replica from it's persistent list.
Change-Id: I9252ab9d9768b549915d8cccf46f102127d97945
Signed-off-by: Moiz Raja <moraja@cisco.com>