Initialize vbucket output parameter in tap.
Initialize vbucket output parameter in tap.

Change-Id: I3e18f2ad607d4aeffed8b7bebc32023c06868851
Reviewed-on: http://review.membase.org/4024
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

membase/ep-engine,couchbase/ep-engine,zbase/ep-engine,hisundar/ep-engine,couchbaselabs/ep-engine,jimwwalker/ep-engine,teligent-ru/ep-engine,jimwwalker/ep-engine,daverigby/kv_engine,daverigby/kv_engine,abhinavdangeti/ep-engine,zbase/ep-engine,teligent-ru/ep-engine,couchbaselabs/ep-engine,couchbase/ep-engine,sriganes/ep-engine,owendCB/ep-engine,daverigby/kv_engine,teligent-ru/ep-engine,couchbaselabs/ep-engine,couchbaselabs/ep-engine,hisundar/ep-engine,daverigby/kv_engine,jimwwalker/ep-engine,sriganes/ep-engine,membase/ep-engine,abhinavdangeti/ep-engine,membase/ep-engine,couchbase/ep-engine,abhinavdangeti/ep-engine,daverigby/ep-engine,couchbase/ep-engine,abhinavdangeti/ep-engine,sriganes/ep-engine,owendCB/ep-engine,teligent-ru/ep-engine,daverigby/ep-engine,zbase/ep-engine,abhinavdangeti/ep-engine,hisundar/ep-engine,couchbaselabs/ep-engine,owendCB/ep-engine,zbase/ep-engine,jimwwalker/ep-engine,membase/ep-engine,daverigby/ep-engine,hisundar/ep-engine,sriganes/ep-engine,daverigby/ep-engine,zbase/ep-engine,owendCB/ep-engine