NCBC-558: Add Thread Synchronization to ClusterManager and Provider classes

Change-Id: I80344f07d54e41eb6cc02b25d0d7896d5054187f
Reviewed-on: http://review.couchbase.org/39761
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>