Form: Do not create a new instance of Url when setting the action

We're shifting parameters and by creating a new instance we'll lose
such changes.

refs #8758

library/Icinga/Web/Form.php

@@ -615,7 +615,7 @@ class Form extends Zend_Form
                 // TODO(el): Re-evalute this necessity. JavaScript could use the container's URL if there's no action set.
                 // We MUST set an action as JS gets confused otherwise, if
                 // this form is being displayed in an additional column
-                $this->setAction(Url::fromRequest()->without(array_keys($this->getElements())));
+                $this->setAction($this->getRequest()->getUrl()->without(array_keys($this->getElements())));
             }
 
             $this->created = true;