handle ns_config:search_with_vclock inside ns_config:run_txn body

Change-Id: Ib984cb2921f8e516f194bac9dc5a0f178306a782
Reviewed-on: http://review.couchbase.org/44498
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>