test: Fix flaky wallet_basic test

Co-authored-by: João Barbosa <joao.paulo.barbosa@gmail.com>

test/functional/wallet_basic.py

@@ -596,6 +596,9 @@ class WalletTest(BitcoinTestFramework):
         # wait until the wallet has submitted all transactions to the mempool
         self.wait_until(lambda: len(self.nodes[0].getrawmempool()) == chainlimit * 2)
 
+        # Prevent potential race condition when calling wallet RPCs right after restart
+        self.nodes[0].syncwithvalidationinterfacequeue()
+
         node0_balance = self.nodes[0].getbalance()
         # With walletrejectlongchains we will not create the tx and store it in our wallet.
         assert_raises_rpc_error(-6, "Transaction has too long of a mempool chain", self.nodes[0].sendtoaddress, sending_addr, node0_balance - Decimal('0.01'))