MB-9311: Notify all the pending connections on vbucket delete

If a given vbucket is deleted, we should notify it to all of its
pending connections, so that the connections are released
immediately and the error messages should be sent to the clients.

Change-Id: Ic230a803f0b26944f98e84ed4d21f8d834e3a561
Reviewed-on: http://review.couchbase.org/30353
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>