NCBC-395: Assign each client instance an identifer

Change-Id: Ib20248cb80a0a88e6de8c87c54f5176e85449f63
Reviewed-on: http://review.couchbase.org/33691
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>