Fix intermittent failure in TestReliableMessageProtocol. (#9927)

We are ending up with queued retransmits on both the initiator and
responder.  The responder has a much longer retransmit interval, but
when we sleep for the initiator to retransmit, we can end up sleeping
too long, so the responder retransmits too.  Make the test handle both
cases.

src/messaging/tests/TestReliableMessageProtocol.cpp

@@ -1226,18 +1226,34 @@ void CheckLostResponseWithPiggyback(nlTestSuite * inSuite, void * inContext)
     // We resent our first message, which did not make it to the app-level
     // listener on the receiver (because it's a duplicate) but did trigger a
     // standalone ack.
-    NL_TEST_ASSERT(inSuite, gLoopback.mSentMessageCount == 4);
-    NL_TEST_ASSERT(inSuite, gLoopback.mDroppedMessageCount == 1);
-    NL_TEST_ASSERT(inSuite, !mockSender.IsOnMessageReceivedCalled);
-    NL_TEST_ASSERT(inSuite, !mockReceiver.IsOnMessageReceivedCalled);
-    NL_TEST_ASSERT(inSuite, rm->TestGetCountRetransTable() == 1);
+    //
+    // Now the annoying part is that depending on how long we _actually_ slept
+    // we might have also triggered the retransmit from the other side, even
+    // though we did not want to.  Handle both cases here.
+    NL_TEST_ASSERT(inSuite, gLoopback.mSentMessageCount == 4 || gLoopback.mSentMessageCount == 6);
+    if (gLoopback.mSentMessageCount == 4)
+    {
+        // Just triggered the retransmit from the sender.
+        NL_TEST_ASSERT(inSuite, gLoopback.mDroppedMessageCount == 1);
+        NL_TEST_ASSERT(inSuite, !mockSender.IsOnMessageReceivedCalled);
+        NL_TEST_ASSERT(inSuite, !mockReceiver.IsOnMessageReceivedCalled);
+        NL_TEST_ASSERT(inSuite, rm->TestGetCountRetransTable() == 1);
+    }
+    else
+    {
+        // Also triggered the retransmit from the receiver.
+        NL_TEST_ASSERT(inSuite, gLoopback.mDroppedMessageCount == 1);
+        NL_TEST_ASSERT(inSuite, mockSender.IsOnMessageReceivedCalled);
+        NL_TEST_ASSERT(inSuite, !mockReceiver.IsOnMessageReceivedCalled);
+        NL_TEST_ASSERT(inSuite, rm->TestGetCountRetransTable() == 0);
+    }
 
     // 1 tick is 64 ms, sleep 65*3 ms to trigger re-transmit from receiver
     test_os_sleep_ms(65 * 3);
     ReliableMessageMgr::Timeout(&ctx.GetSystemLayer(), rm);
 
-    // We resent our response message, which should show up as an app-level
-    // message and trigger a standalone ack.
+    // And now we've definitely resent our response message, which should show
+    // up as an app-level message and trigger a standalone ack.
     NL_TEST_ASSERT(inSuite, gLoopback.mSentMessageCount == 6);
     NL_TEST_ASSERT(inSuite, gLoopback.mDroppedMessageCount == 1);
     NL_TEST_ASSERT(inSuite, mockSender.IsOnMessageReceivedCalled);