title: Symfony2 : onKernelResponse called twice as MASTER_REQUEST
body: <p>I'm using the event listener <code>onKernelResponse</code>.</p>
  <p>I used :</p>
  <pre><code>if (HttpKernelInterface::MASTER_REQUEST != $event-&gt;getRequestType()) {
      return;
  }
  </code></pre>
  <p>It's having a <code>MASTER_REQUEST</code> twice in my action, there is one before the <code>&lt;!DOCTYPE html&gt; &lt;html&gt; &lt;head&gt;</code>etc, and the other one as excepted after the end of the layout.</p>
  <p>He is my <code>services.yml</code> :</p>
  <pre class="lang-yaml prettyprint-override"><code>history.listener:
      class: VENDOR\MyBundle\Service\HistoryListener
      arguments: [@doctrine.orm.entity_manager, @logger, @history]
      tags:
          - { name: kernel.event_listener, event: kernel.controller, method: onKernelController }
          - { name: kernel.event_listener, event: kernel.response, method: onKernelResponse }
  </code></pre>
  <p>Did I do something wrong?</p>