Merge #20322: test: Fix intermittent issue in wallet_listsinceblock

4444128 test: Fix intermittent issue in wallet_listsinceblock (MarcoFalke)

Pull request description:

ACKs for top commit:
  Empact:
    Code Review ACK bitcoin/bitcoin@4444128

Tree-SHA512: 86d47b1e3c8681dd479654589c894016ac81a3c96a34c3b4a75278b2af85054ea8c6f768e518a5322a4928d82d5e99105bbce0f4fa6a7a18c40e3e0799f9ab54

Author: MarcoFalke

test/functional/wallet_listsinceblock.py

@@ -191,6 +191,7 @@ def test_double_spend(self):
         address = key_to_p2wpkh(eckey.get_pubkey().get_bytes())
         self.nodes[2].sendtoaddress(address, 10)
         self.nodes[2].generate(6)
+        self.sync_all()
         self.nodes[2].importprivkey(privkey)
         utxos = self.nodes[2].listunspent()
         utxo = [u for u in utxos if u["address"] == address][0]