The XML generation of service is broken for form types

[stof]

For a form type, it generates the following snippet:

<service class="Incenteev\WebBundle\Form\Type\SuffixedTextType" id="incenteev.form.suffixed_text">
  <tags alias="incenteev_suffixed_text" name="form.type"/>
</service>

this is wrong. It should be <tag>, not <tags>