title: `docker pull` returns `denied: access forbidden` from private gitlab registry
body: <p>I have a <code>Dockerfile</code> which is going to be implemented <code>FROM</code> a private registry's image. I build this file without any problem with <code>Docker version 1.12.6, build 78d1802</code> and <code>docker-compose version 1.8.0, build unknown</code>, but in another machine which has <code>Docker version 17.06.1-ce, build 874a737</code> and <code>docker-compose version 1.16.1, build 6d1ac21</code>, the <code>docker-compose build</code> returns:</p>
  
  <pre><code>FROM my.private.gitlab.registry:port/image:tag
  http://my.private.gitlab.registry:port/v2/docker/image/manifests/tag: denied: access forbidden
  </code></pre>
  
  <p><code>docker pull my.private.gitlab.registry:port/image:tag</code> returns the same. </p>
  
  <p>Notice that I tried to get <code>my.private.registry:port/image:tag</code> and <code>http://my.private.registry:port/v2/docker/image/manifests/tag</code> has been catched.</p>