Runs cron and reloads the page.
public function submitCron(array &$form, array &$form_state) {
// Run cron manually from Cron form.
if (drupal_cron_run()) {
drupal_set_message(t('Cron run successfully.'));
}
else {
drupal_set_message(t('Cron run failed.'), 'error');
}
return new RedirectResponse(url('admin/config/system/cron', array(
'absolute' => TRUE,
)));
}