test: fix inconsistency in fundrawtransaction weight limits test

Currently, the test is passing due to a mistake in the test inputs
selection process. We are selecting the parent transaction change
output as one of the inputs of the transaction to fund, which
helps to surpass the target amount when it shouldn't due to the
fee reduction.

The failure arises when the test behaves as intended by its coder;
that is, when it does not select the change output. In this case,
the pre-selected inputs aren't enough to cover the target amount.

Fix this by excluding the parent transaction's change output from
the inputs selection and including an extra input to cover the tx
fee.

test/functional/wallet_fundrawtransaction.py

@@ -1322,15 +1322,15 @@ class RawTransactionsTest(BitcoinTestFramework):
         outputs = []
         for _ in range(1472):
             outputs.append({wallet.getnewaddress(address_type="legacy"): 0.1})
-        txid = self.nodes[0].send(outputs=outputs)["txid"]
+        txid = self.nodes[0].send(outputs=outputs, change_position=0)["txid"]
         self.generate(self.nodes[0], 1)
 
         # 272 WU per input (273 when high-s); picking 1471 inputs will exceed the max standard tx weight.
         rawtx = wallet.createrawtransaction([], [{wallet.getnewaddress(): 0.1 * 1471}])
 
-        # 1) Try to fund transaction only using the preset inputs
+        # 1) Try to fund transaction only using the preset inputs (pick all 1472 inputs to cover the fee)
         input_weights = []
-        for i in range(1471):
+        for i in range(1, 1473):  # skip first output as it is the parent tx change output
             input_weights.append({"txid": txid, "vout": i, "weight": 273})
         assert_raises_rpc_error(-4, "Transaction too large", wallet.fundrawtransaction, hexstring=rawtx, input_weights=input_weights)