title: Symfony default locale without specifying in URL
body: <p>I would like to configure the Symfony <code>locale</code> options so that I can successfully access the following routes:</p>
  
  <pre><code>/route
  /{locale}/route
  </code></pre>
  
  <p>Currently, I can access <code>/{locale}/route</code> and I get my view, however, <code>/route</code> returns a <code>No route found for "GET /route"</code>.  My configuration is as follows:</p>
  
  <pre><code>#app/config/parameters.yml
  parameters:
      locale: en
  
  #app/config/config.yml
  parameters:
      app_locales: en|fr
  framework:
      translator: { fallback: "%locale%" }
      default_locale: "%locale%"
  
  #app/config/routing.yml
  app:
      resource: '@AppBundle/Controller/'
      type: annotation
  </code></pre>
  
  <p>My Controller has the following annotations:</p>
  
  <pre><code>#src/AppBundle/Controller/Admin/MyController.php
  /**
   *
   * @Route(
   *     "/{_locale}/admin/my",
   *     defaults={"_locale":"%locale%"},
   *     requirements={"_locale":"%app_locales%"}
   *     )
   */
  class MyController extends Controller
  {
      /**
       * @Route("/", name="admin_my_list")
       * @Method("GET")
       */
      public function listAction()
      {
          ...
      }
  }
  </code></pre>
  
  <p>If I specifically include the <code>locale</code>, it all works.  If I exclude the <code>locale</code>, I get the <code>No route found</code> error.</p>