db: set RFDontFillCache read flag when creating compaction iterator
db: set RFDontFillCache read flag when creating compaction iterator

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