test: Fix intermittent failure in wallet_basic.py

There could be a race with outstanding TxAddedToMempool notifications
being applied to the soon-to-be created wallet.

Fixes an intermittent timeout reproducable by adding a sleep to
AddToWallet.

Author: mzumsande

test/functional/wallet_basic.py

@@ -603,6 +603,8 @@ def run_test(self):
         txid_a = self.nodes[0].sendtoaddress(addr_a, 0.01)
         txid_b = self.nodes[0].sendtoaddress(addr_b, 0.01)
         self.generate(self.nodes[0], 1, sync_fun=self.no_op)
+        # Prevent race of listunspent with outstanding TxAddedToMempool notifications
+        self.nodes[0].syncwithvalidationinterfacequeue()
         # Now import the descriptors, make sure we can identify on which descriptor each coin was received.
         self.nodes[0].createwallet(wallet_name="wo", descriptors=True, disable_private_keys=True)
         wo_wallet = self.nodes[0].get_wallet_rpc("wo")