title: 401 error on Wordpress wp-admin access with NGINX backend
body: <p>I have apache working on domain.com:81. Wordpress website is configured to domain.com.
  I've added nginx as static cache front-end on domain.com:80
  And now website is loading fine, while i can not access wp-admin with a such error:</p>
  
  <pre><code>401 Authorization Required
  
  This server could not verify that you are authorized to access the document requested. Either you supplied the wrong credentials (e.g., bad password), or your browser doesn't understand how to supply the credentials required.
  </code></pre>
  
  <p>and also something about 'Subdomain authorization'.
  P.S. I have another site running on the same hosting (opencart, yii), they are working with the same nginx config (static is cached, other responses are redirected to proxy_pass), and they are working well.</p>