test: Fix intermittent issue in p2p_feefilter

test/functional/p2p_feefilter.py

@@ -111,6 +111,7 @@ class FeeFilterTest(BitcoinTestFramework):
         txids = [miniwallet.send_self_transfer(fee_rate=Decimal('0.00020000'), from_node=node0)['wtxid'] for _ in range(3)]
         conn.wait_for_invs_to_match(txids)
         conn.clear_invs()
+        self.sync_mempools()  # must be sure node 1 has received all txs
 
         self.log.info("Remove fee filter and check txs are received again")
         conn.send_and_ping(msg_feefilter(0))