panel-buttons: Remove transitions for corner buttons

So far transitions do not work for the custom drawn corners, so to
avoid a visible glitch when transitioning a button in the panel corner
while updating the style of the apparently attached corner instantly,
remove transition of those panel buttons until we make it work for the
custom drawn parts as well.

https://bugzilla.gnome.org/show_bug.cgi?id=642697

js/ui/panel.js

@@ -871,6 +871,7 @@ Panel.prototype = {
         this._rightBox.add(this._statusBox);
 
         this._statusmenu = new StatusMenu.StatusMenuButton();
+        this._statusmenu.actor.name = 'panelStatus';
         this._menus.addMenu(this._statusmenu.menu);
         this._rightBox.add(this._statusmenu.actor);