Build form early and reactivate ajaxy replacing

This makes subform validation work for everything again. I also had to slightly unhack the corresponding js. It's still not very nice in that it still reloads even though ajax would have been enough but I could figure out why the mast source field was not getting the proper values (You can reproduce this by commenting the window.location.reload() in the js).

airtime_mvc/application/forms/LiveStreamingPreferences.php

@@ -144,12 +144,4 @@ class Application_Form_LiveStreamingPreferences extends Zend_Form_SubForm
             )
         );
     }
-
-
-    public function isValid($data)
-    {
-        $isValid = parent::isValid($data);
-
-        return $isValid;
-    }
 }