tests: wallet_basic lock needed unspents

To avoid accidentally spending UTXOs that are needed later in the test,
lock those UTXOs after they're creation.

Author: achow101

test/functional/wallet_basic.py

@@ -13,6 +13,7 @@
     assert_equal,
     assert_fee_amount,
     assert_raises_rpc_error,
+    find_vout_for_address,
 )
 from test_framework.wallet_util import test_address
 
@@ -427,6 +428,9 @@ def run_test(self):
             # 1. Send some coins to generate new UTXO
             address_to_import = self.nodes[2].getnewaddress()
             txid = self.nodes[0].sendtoaddress(address_to_import, 1)
+            self.sync_mempools(self.nodes[0:3])
+            vout = find_vout_for_address(self.nodes[2], txid, address_to_import)
+            self.nodes[2].lockunspent(False, [{"txid": txid, "vout": vout}])
             self.generate(self.nodes[0], 1)
             self.sync_all(self.nodes[0:3])