copy statedb every time use it

Author: TraceBundy

consensus/cbft/context/context.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"github.com/PlatONnetwork/PlatON-Go/consensus"
 	ctypes "github.com/PlatONnetwork/PlatON-Go/consensus/cbft/types"
+	"github.com/PlatONnetwork/PlatON-Go/core/state"
 	"github.com/PlatONnetwork/PlatON-Go/p2p/enode"
 	"sync/atomic"
 	"time"
@@ -132,7 +133,7 @@ func (ctx *Context) StateDB() sdk.StateDBReader {
 		return nil
 	}
 	if s := ctx.statedb.Load(); s != nil {
-		return s.(types.StateDBReader)
+		return s.(sdk.StateDBReader).(*state.StateDB).NewStateDB()
 	}
 	state, _ := ctx.cbft.GetState(ctx.Header())
 	ctx.statedb.Store(state)