Form\View\Helper\FormRow label position gets overwritten by __invoke()

[stefanotorresi]

I noticed this when using the Form view helper, which in turn invokes FormRow helper passing only the element.

// inside view template
$this->formRow()->setLabelPosition('append');

/** @var Zend\Form\Form $form */
echo $this->form($form); // this does actually output prepended labels