cmd/utils, core: disable exp diff for olympic net

cmd/utils/cmd.go

@@ -21,6 +21,7 @@ import (
 	"bufio"
 	"fmt"
 	"io"
+	"math"
 	"math/big"
 	"os"
 	"os/signal"
@@ -152,6 +153,7 @@ func InitOlympic() {
 	params.MaximumExtraDataSize = big.NewInt(1024)
 	NetworkIdFlag.Value = 0
 	core.BlockReward = big.NewInt(1.5e+18)
+	core.ExpDiffPeriod = big.NewInt(math.MaxInt64)
 }
 
 func FormatTransactionData(data string) []byte {