Add stream end to list of expected ack messages

Change-Id: Ibf20b96e24dd52c7bacb96c17828c3db80b5f5e5
Reviewed-on: http://review.couchbase.org/33464
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>