MB-8663 Mention where to find replication id.

Change-Id: I1902d5d04ee6ab020c7df491b86b3c9889e64da3
Reviewed-on: http://review.couchbase.org/28584
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>