test: create wallet specific for test_locked_wallet case

Other tests are also relying on the node1 default wallet,
which thanks to 'test_locked_wallet' is encrypted.
And can only be accessed within a specific timeframe (100ms)
set internally by the same test.

This make other tests susceptible to races. They can only
perform their operations successfully within the specified
time.

This can be seen running the test in valgrind, where other
test cases fail due the wallet re-locking itself after the
100ms.

test/functional/wallet_fundrawtransaction.py

@@ -581,11 +581,20 @@ def test_spend_2of2(self):
     def test_locked_wallet(self):
         self.log.info("Test fundrawtxn with locked wallet and hardened derivation")
 
-        self.nodes[1].encryptwallet("test")
+        df_wallet = self.nodes[1].get_wallet_rpc(self.default_wallet_name)
+        self.nodes[1].createwallet(wallet_name="locked_wallet", descriptors=self.options.descriptors)
+        wallet = self.nodes[1].get_wallet_rpc("locked_wallet")
+
+        # Add some balance to the wallet (this will be reverted at the end of the test)
+        df_wallet.sendall(recipients=[wallet.getnewaddress()])
+        self.generate(self.nodes[1], 1)
+
+        # Encrypt wallet and import descriptors
+        wallet.encryptwallet("test")
 
         if self.options.descriptors:
-            self.nodes[1].walletpassphrase('test', 10)
-            self.nodes[1].importdescriptors([{
+            wallet.walletpassphrase('test', 10)
+            wallet.importdescriptors([{
                 'desc': descsum_create('wpkh(tprv8ZgxMBicQKsPdYeeZbPSKd2KYLmeVKtcFA7kqCxDvDR13MQ6us8HopUR2wLcS2ZKPhLyKsqpDL2FtL73LMHcgoCL7DXsciA8eX8nbjCR2eG/0h/*h)'),
                 'timestamp': 'now',
                 'active': True
@@ -596,49 +605,57 @@ def test_locked_wallet(self):
                 'active': True,
                 'internal': True
             }])
-            self.nodes[1].walletlock()
+            wallet.walletlock()
 
         # Drain the keypool.
-        self.nodes[1].getnewaddress()
-        self.nodes[1].getrawchangeaddress()
+        wallet.getnewaddress()
+        wallet.getrawchangeaddress()
 
-        # Choose 2 inputs
-        inputs = self.nodes[1].listunspent()[0:2]
-        value = sum(inp["amount"] for inp in inputs) - Decimal("0.00000500") # Pay a 500 sat fee
+        # Choose input
+        inputs = wallet.listunspent()
+        # Deduce fee to produce a changeless transaction
+        value = inputs[0]["amount"] - Decimal("0.00002200")
         outputs = {self.nodes[0].getnewaddress():value}
-        rawtx = self.nodes[1].createrawtransaction(inputs, outputs)
+        rawtx = wallet.createrawtransaction(inputs, outputs)
         # fund a transaction that does not require a new key for the change output
-        self.nodes[1].fundrawtransaction(rawtx)
+        funded_tx = wallet.fundrawtransaction(rawtx)
+        assert_equal(funded_tx["changepos"], -1)
 
         # fund a transaction that requires a new key for the change output
         # creating the key must be impossible because the wallet is locked
         outputs = {self.nodes[0].getnewaddress():value - Decimal("0.1")}
-        rawtx = self.nodes[1].createrawtransaction(inputs, outputs)
-        assert_raises_rpc_error(-4, "Transaction needs a change address, but we can't generate it.", self.nodes[1].fundrawtransaction, rawtx)
+        rawtx = wallet.createrawtransaction(inputs, outputs)
+        assert_raises_rpc_error(-4, "Transaction needs a change address, but we can't generate it.", wallet.fundrawtransaction, rawtx)
 
         # Refill the keypool.
-        self.nodes[1].walletpassphrase("test", 100)
-        self.nodes[1].keypoolrefill(8) #need to refill the keypool to get an internal change address
-        self.nodes[1].walletlock()
+        wallet.walletpassphrase("test", 100)
+        wallet.keypoolrefill(8) #need to refill the keypool to get an internal change address
+        wallet.walletlock()
 
-        assert_raises_rpc_error(-13, "walletpassphrase", self.nodes[1].sendtoaddress, self.nodes[0].getnewaddress(), 1.2)
+        assert_raises_rpc_error(-13, "walletpassphrase", wallet.sendtoaddress, self.nodes[0].getnewaddress(), 1.2)
 
         oldBalance = self.nodes[0].getbalance()
 
         inputs = []
         outputs = {self.nodes[0].getnewaddress():1.1}
-        rawtx = self.nodes[1].createrawtransaction(inputs, outputs)
-        fundedTx = self.nodes[1].fundrawtransaction(rawtx)
+        rawtx = wallet.createrawtransaction(inputs, outputs)
+        fundedTx = wallet.fundrawtransaction(rawtx)
+        assert fundedTx["changepos"] != -1
 
         # Now we need to unlock.
-        self.nodes[1].walletpassphrase("test", 600)
-        signedTx = self.nodes[1].signrawtransactionwithwallet(fundedTx['hex'])
-        self.nodes[1].sendrawtransaction(signedTx['hex'])
+        wallet.walletpassphrase("test", 600)
+        signedTx = wallet.signrawtransactionwithwallet(fundedTx['hex'])
+        wallet.sendrawtransaction(signedTx['hex'])
         self.generate(self.nodes[1], 1)
 
         # Make sure funds are received at node1.
         assert_equal(oldBalance+Decimal('51.10000000'), self.nodes[0].getbalance())
 
+        # Restore pre-test wallet state
+        wallet.sendall(recipients=[df_wallet.getnewaddress(), df_wallet.getnewaddress(), df_wallet.getnewaddress()])
+        wallet.unloadwallet()
+        self.generate(self.nodes[1], 1)
+
     def test_many_inputs_fee(self):
         """Multiple (~19) inputs tx test | Compare fee."""
         self.log.info("Test fundrawtxn fee with many inputs")