db: snapshot: check for snapshot release status
db: snapshot: check for snapshot release status

zzl0/goleveldb,chai2010/goleveldb,FactomProject/goleveldb,no2key/goleveldb,hustbill/goleveldb,ngaut/goleveldb,trigrass2/goleveldb,conseweb/goleveldb,rentongzhang/goleveldb,syndtr/goleveldb,btcsuite/goleveldb