Return not found for get when db file doesn't exist
Return not found for get when db file doesn't exist

If we are asking couchstore for an item then that means
we have already checked to see if the vbucket exists. If
it doesn't exist on disk then we should return not found
instead of not my vbucket.

Change-Id: I83bba04176b716e9381a2aefdf5fdc1b8081218a
Reviewed-on: http://review.couchbase.org/20281
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Reviewed-by: Jin Lim <c45cd80a556f432a3607171a6818cd5a074b5cd4@couchbase.com>
Tested-by: Michael Wiederhold <a17fed27eaa842282862ff7c1b9c8395a26ac320@couchbase.com>

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