MB-8726: added ns_server:search_with_vclock/2

Change-Id: I21747b5ad06807d493d0a20f59795874cf30aee7
Reviewed-on: http://review.couchbase.org/29999
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>