Account the effective gas price for frontier transactions after EIP-1559 fork (#1862)

* fix consensus issue.
ensure that gas price is greater than base fee for frontier transactions

Signed-off-by: Abdelhamid Bakhta <abdelhamid.bakhta@consensys.net>

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/core/fees/TransactionPriceCalculator.java

@@ -32,14 +32,14 @@ public interface TransactionPriceCalculator {
 
   static TransactionPriceCalculator eip1559() {
     return (transaction, maybeBaseFee) -> {
+      ExperimentalEIPs.eip1559MustBeEnabled();
+      final Wei baseFee = Wei.of(maybeBaseFee.orElseThrow());
       if (transaction.getType().equals(TransactionType.FRONTIER)) {
         return transaction.getGasPrice();
       }
-      ExperimentalEIPs.eip1559MustBeEnabled();
       final Wei gasPremium =
           Wei.of((BigInteger) transaction.getGasPremium().orElseThrow().getValue());
       final Wei feeCap = Wei.of((BigInteger) transaction.getFeeCap().orElseThrow().getValue());
-      final Wei baseFee = Wei.of(maybeBaseFee.orElseThrow());
       Wei price = gasPremium.add(baseFee);
       if (price.compareTo(feeCap) > 0) {
         price = feeCap;