MB-10489 Register the seq_num based replication cursor correctly.

Change-Id: I511ff81b5b519602d262984c370952f0074d0788
Reviewed-on: http://review.couchbase.org/34747
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: buildbot <build@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>