title: Session lost during impersonation
body: <p>I use SonataAdminBundle with configured <code>sonata_user</code> in <code>config.yml</code>:</p>
  
  <pre><code>sonata_user:
      impersonating:
          route:        _profile_logged
      # more config
  </code></pre>
  
  <p>I have my admin panel under <code>/admin</code> prefix. I've configured <code>UserAdmin</code> (based on <code>User</code> entity) with <code>impersonating</code> field. I've tried to go to impersonate user by clicked link in my admin panel and I saw application (not admin panel) login page.</p>
  
  <p>I checked developer toolbar and I noticed that request for impersonate user was redirected to login page. It's quite strange, because this request has mostly same parameters like previous one (for user list in admin panel). Especially <code>Request Cookies</code> section is identical.</p>
  
  <p>I noticed one difference in <code>Request Headers</code>: first one request (for user list in admin panel) send <code>cache-control max-age=0</code> but second one (for impersonate) dosen't.</p>
  
  <p>Obviously, I logged to admin panel on user with full permissions (particularly <code>ROLE_ALLOWED_TO_SWITCH</code>). </p>
  
  <p>So, how can I do impersonate directly from admin panel? What could be wrong in my app?</p>