use maxint-2 to signal RBF, in order to standardize with Bitcoin Core

lib/commands.py

@@ -414,7 +414,7 @@ class Commands:
         coins = self.wallet.get_spendable_coins(domain)
         tx = self.wallet.make_unsigned_transaction(coins, final_outputs, self.config, fee, change_addr)
         if rbf:
-            tx.set_sequence(0)
+            tx.set_rbf(True)
         if not unsigned:
             self.wallet.sign_transaction(tx, self._password)
         return tx

lib/transaction.py

@@ -681,9 +681,10 @@ class Transaction:
         s += int_to_hex(txin.get('sequence', 0xffffffff), 4)
         return s
 
-    def set_sequence(self, n):
+    def set_rbf(self, rbf):
+        nSequence = 0xffffffff - (2 if rbf else 0)
         for txin in self.inputs():
-            txin['sequence'] = n
+            txin['sequence'] = nSequence
 
     def BIP_LI01_sort(self):
         # See https://github.com/kristovatlas/rfc/blob/master/bips/bip-li01.mediawiki