kbd-status: Close the menu when switching layouts

Layout items in the menu overwrite PopupBaseMenuItem.activate(),
so the menu stays open when selecting a layout from the menu.
Chain up to the parent class' method to make the items behave properly.

https://bugzilla.gnome.org/show_bug.cgi?id=639474

js/ui/status/keyboard.js

@@ -36,6 +36,7 @@ LayoutMenuItem.prototype = {
     },
 
     activate: function(event) {
+        PopupMenu.PopupBaseMenuItem.prototype.activate.call(this);
         this._config.lock_group(this._id);
     }
 };