MB-10400: use better api for opening src master vbucket
MB-10400: use better api for opening src master vbucket

Change-Id: I93ce7bab82c53b56cbc4ea5c0606a9c2fe370b60
Reviewed-on: http://review.couchbase.org/34810
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

daverigby/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,ceejatec/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,membase/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,membase/ns_server,mschoch/ns_server,mschoch/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,membase/ns_server,mschoch/ns_server,mschoch/ns_server,daverigby/ns_server,nimishzynga/ns_server,ceejatec/ns_server