fix(test): avoid race condition in TwoBrokerVirtualTopicSelectorAwareForwardingTest (#1951)

Replace bare assertEquals with Wait.waitFor for the queue depth check in
testSelectorAwareForwarding. The broker decrements its messages counter only
after processing the MessageAck asynchronously, so asserting immediately after
waitForMessagesToArrive could fire before the ACK is processed on a loaded CI runner.

Author: jbonofre

activemq-unit-tests/src/test/java/org/apache/activemq/usecases/TwoBrokerVirtualTopicSelectorAwareForwardingTest.java

@@ -520,10 +520,11 @@ public void testSelectorAwareForwarding() throws Exception {
         assertEquals(2, msgsB.getMessageCount());
 
 
-        // queue should be drained
-        assertEquals(0, brokerB.getDestination(new ActiveMQQueue("Consumer.B.VirtualTopic.tempTopic"))
-                .getDestinationStatistics().getMessages().getCount());
-        // and the enqueue count for the remote queue should only be 1
+        // queue should be drained - use Wait.waitFor to allow broker ACK processing to complete
+        assertTrue("queue should be drained after consumer ACKs", Wait.waitFor(() ->
+                brokerB.getDestination(new ActiveMQQueue("Consumer.B.VirtualTopic.tempTopic"))
+                        .getDestinationStatistics().getMessages().getCount() == 0, 5000, 100));
+        // and the enqueue count for the remote queue should only be 3
         assertEquals(3, brokerB.getDestination(new ActiveMQQueue("Consumer.B.VirtualTopic.tempTopic"))
                 .getDestinationStatistics().getEnqueues().getCount());