test: Fix intermittent issue in wallet_send

test/functional/wallet_send.py

@@ -316,6 +316,7 @@ class WalletSendTest(BitcoinTestFramework):
         res = self.nodes[0].sendrawtransaction(hex)
         self.nodes[0].generate(1)
         assert_equal(self.nodes[0].gettransaction(txid)["confirmations"], 1)
+        self.sync_all()
 
         self.log.info("Lock unspents...")
         utxo1 = w0.listunspent()[0]