Make sure upr mutation/deletion messages by_seqno's increase

Change-Id: I6837d68fdfc798c5e4203080f271c62137acaaf4
Reviewed-on: http://review.couchbase.org/32897
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>