MXS-2815: Downgrade O_DIRECT from warning to notice

There's no real action the user can take which is why it shouldn't be a
warning.

maxutils/maxbase/src/messagequeue.cc

@@ -132,8 +132,7 @@ MessageQueue* MessageQueue::create(Handler* pHandler)
         if (rv == 0)
         {
             // Succeeded, so apparently it was the missing support for O_DIRECT.
-            MXB_WARNING("Platform does not support O_DIRECT in conjunction with pipes, "
-                        "using without.");
+            MXB_NOTICE("Platform does not support O_DIRECT in conjunction with pipes, using without.");
         }
     }