Add Mapping keys to post account (OffchainLabs#5)

Author: lwedge99

eth/tracers/sentio/prestate.go

@@ -211,7 +211,7 @@ func (t *sentioPrestateTracer) CaptureTxEnd(restGas uint64) {
 		newNonce := t.env.StateDB.GetNonce(addr)
 		newCode := t.env.StateDB.GetCode(addr)
 		postAccount.CodeAddress = state.CodeAddress
-		postAccount.MappingKeys = state.MappingKeys
+		postAccount.MappingKeys = t.pre[addr].MappingKeys
 
 		if newBalance.Cmp(t.pre[addr].Balance) != 0 {
 			modified = true