NCBC-255: Implement Unlock without CAS operation

Change-Id: I182a7283efb89d88d0a224c780157d2bc5fc969e
Reviewed-on: http://review.couchbase.org/26013
Reviewed-by: Saakshi Manocha <saakshi.manocha@globallogic.com>
Tested-by: Saakshi Manocha <saakshi.manocha@globallogic.com>