title: Symfony does not show private services in debug:container --show-private
body: <p>Running </p>
  
  <pre><code>app/console debug:container --show-private 
  </code></pre>
  
  <p>does not list the services declared with <code>public: false</code> e.g:</p>
  
  <pre><code> another_service:
          public: false
          class: MineBundle\Service\FirstService
  </code></pre>
  
  <p>But, If I run <code>app/console debug:container --show-private | wc -l</code> and <code>app/console debug:container | wc -l</code> I will get different results.</p>
  
  <p>Tried with symfony 2.8 and 3.1 and got same behaviour. </p>
  
  <p>Any idea?</p>
  
  <p>Thanks!</p>