[release/1.3.4] cmd/utils: lower the min accepted gas price for relay and GPO to 20 shannon

(cherry picked from commit ab92678fb3)

cmd/utils/flags.go

@@ -183,7 +183,7 @@ var (
 	GasPriceFlag = cli.StringFlag{
 		Name:  "gasprice",
 		Usage: "Minimal gas price to accept for mining a transactions",
-		Value: new(big.Int).Mul(big.NewInt(50), common.Shannon).String(),
+		Value: new(big.Int).Mul(big.NewInt(20), common.Shannon).String(),
 	}
 	ExtraDataFlag = cli.StringFlag{
 		Name:  "extradata",
@@ -356,7 +356,7 @@ var (
 	GpoMinGasPriceFlag = cli.StringFlag{
 		Name:  "gpomin",
 		Usage: "Minimum suggested gas price",
-		Value: new(big.Int).Mul(big.NewInt(50), common.Shannon).String(),
+		Value: new(big.Int).Mul(big.NewInt(20), common.Shannon).String(),
 	}
 	GpoMaxGasPriceFlag = cli.StringFlag{
 		Name:  "gpomax",