Use createrawtx locktime parm in txn_clone

Streamlines the test and serves as a test of the createrawtransaction
locktime parameter.

qa/rpc-tests/txn_clone.py

@@ -57,16 +57,10 @@ class TxnMallTest(BitcoinTestFramework):
         clone_inputs = [{"txid":rawtx1["vin"][0]["txid"],"vout":rawtx1["vin"][0]["vout"]}]
         clone_outputs = {rawtx1["vout"][0]["scriptPubKey"]["addresses"][0]:rawtx1["vout"][0]["value"],
                          rawtx1["vout"][1]["scriptPubKey"]["addresses"][0]:rawtx1["vout"][1]["value"]}
-        clone_raw = self.nodes[0].createrawtransaction(clone_inputs, clone_outputs)
+        clone_locktime = rawtx1["locktime"]
+        clone_raw = self.nodes[0].createrawtransaction(clone_inputs, clone_outputs, clone_locktime)
 
-        # 3 hex manipulations on the clone are required
-
-        # manipulation 1. sequence is at version+#inputs+input+sigstub
-        posseq = 2*(4+1+36+1)
-        seqbe = '%08x' % rawtx1["vin"][0]["sequence"]
-        clone_raw = clone_raw[:posseq] + seqbe[6:8] + seqbe[4:6] + seqbe[2:4] + seqbe[0:2] + clone_raw[posseq + 8:]
-
-        # manipulation 2. createrawtransaction randomizes the order of its outputs, so swap them if necessary.
+        # createrawtransaction randomizes the order of its outputs, so swap them if necessary.
         # output 0 is at version+#inputs+input+sigstub+sequence+#outputs
         # 40 BTC serialized is 00286bee00000000
         pos0 = 2*(4+1+36+1+4+1)
@@ -78,11 +72,6 @@ class TxnMallTest(BitcoinTestFramework):
             output1 = clone_raw[pos0 + output_len : pos0 + 2 * output_len]
             clone_raw = clone_raw[:pos0] + output1 + output0 + clone_raw[pos0 + 2 * output_len:]
 
-        # manipulation 3. locktime is after outputs
-        poslt = pos0 + 2 * output_len
-        ltbe = '%08x' % rawtx1["locktime"]
-        clone_raw = clone_raw[:poslt] + ltbe[6:8] + ltbe[4:6] + ltbe[2:4] + ltbe[0:2] + clone_raw[poslt + 8:]
-
         # Use a different signature hash type to sign.  This creates an equivalent but malleated clone.
         # Don't send the clone anywhere yet
         tx1_clone = self.nodes[0].signrawtransaction(clone_raw, None, None, "ALL|ANYONECANPAY")