glocalfilemonitor: Emit notification on rate limit change

The changed variable was previously uninitialised in the path where the
rate limit was actually changed. This could result in the
GObject::notify signal not getting emitted.

Spotted by Coverity.

CID: #1296516

https://bugzilla.gnome.org/show_bug.cgi?id=748834

gio/glocalfilemonitor.c

@@ -466,6 +466,8 @@ g_file_monitor_source_set_rate_limit (GFileMonitorSource *fms,
 
       g_sequence_sort (fms->pending_changes, pending_change_compare_ready_time, fms);
       g_file_monitor_source_update_ready_time (fms);
+
+      changed = TRUE;
     }
   else
     changed = FALSE;