MB-100 Don't torture ns_config for every single replicated doc.

Change-Id: I39745fcb32725356955c8abde05e38691e1602f2
Reviewed-on: http://review.couchbase.org/28173
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>