Move ConnMap::notifyVBConnections to TapConnMap.

ConnMap::notifyVBConnections function is only used by TapConnMap.

Change-Id: If0eec43dc07253fa9c757910bb3ff110512220b3
Reviewed-on: http://review.couchbase.org/39253
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>