Reschedule the vbucket bg fetch task if its DB file is not created
Reschedule the vbucket bg fetch task if its DB file is not created

We might receive getMeta requests for non-existent keys before
their vbucket DB file is created. Therefore, it is required to
reschedule a bg fetch job until the file is created.

Change-Id: I4c692526fceea3b0015728ec40d9d815bc58ff6b
Reviewed-on: http://review.couchbase.org/33221
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

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