[rel-2.5.0] update ns_server reference for MB-9967

Change-Id: I38619747a4769272ba109a28da1b8ca64da72af9
Reviewed-on: http://review.couchbase.org/32708
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>