Removing required attribute on user entity fields not working

<?php
 /**
 * Implements hook_form_alter()
 */
function paypal_signup_form_alter(&$form, &$form_state, $form_id) { 
  if($form_id == 'user_register_form'){
      global $user;
      if(!in_array('administrator', array_values($user->roles))){
        //Submit handler for redirecting user to Paypal.
        $form['#submit'][] = '_paypal_signup_redirect_paypal';
    } else {
        // Remove validation when admin is creating user.
        foreach (element_children($form) as $key) {
            if (strpos($key, 'field_') !== FALSE) {
              $form[$key][LANGUAGE_NONE][0]['#required'] = FALSE;
              $form[$key][LANGUAGE_NONE]['#required'] = FALSE;
            }
         }
        dpm($form);
    } 
  }
}
?>

In the dpm it shows that #required = bool(false) also i tried with integer (0). But still i am getting errors of required fields.
It also shows the * sign on all custom fields which by the code it should not. any one please have a look why the validation still exists. If i go to manage fields on user entity and remove the uncheck the requird checkbox the fields set to be non-required. But i want that when admin is creating user the fields should not be required.

Thanks