MB-6323 attempt to open db with initial rev = 1 if file is not found
MB-6323 attempt to open db with initial rev = 1 if file is not found

Scanning db files, getDbFile(), for a given vbucket id can return
failure during this very narrow period between deleting old db file
and renaming newly compacted db file with new rev number.

Change-Id: If871ba735a95013b41f2ac8e75181efd74453730
Reviewed-on: http://review.couchbase.org/20324
Reviewed-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>
Tested-by: Chiyoung Seo <8b279095f11c26cc21045fda5a3e51debb005aa9@gmail.com>

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