title: Woocommerce - Cannot delete a product variation
body: <p>Using WooCommerce 2.6.1</p>
  
  <p>I cannot delete a product variation for a variable product: the record is still in the database after the ajax call.
  It seems the ajax call doesn't go through: putting error_log(print_r('remove_variation', true)); doesn't output anything (line 387 in class-wc-ajax.php).
  The action is added in the constructor of the class. The function public function remove_variation() is just not called.</p>
  
  <p>Has anyone had the same issue, and found a way to make it work?</p>