title: Why does GetExternalLoginInfoAsync() return null in this case?
body: <p>I created an app using Identity2 MVC5 and Google login to do SSO to Google...</p>
  
  <p>If I login successfully, then close the browser, then log back in , 
  this code block get a loginInfo == null, </p>
  
  <pre><code>public async Task&lt;ActionResult&gt; ExternalLoginCallback(string returnUrl)
          {
              var loginInfo = await AuthenticationManager.GetExternalLoginInfoAsync();
              if (loginInfo == null)
              {
                  return RedirectToAction( "LogOut" );
                  //return RedirectToAction("Login");
              }
  </code></pre>
  
  <p>My best guess is that the asp.net cookie is session and thus deleted, but the Google Oauth token is still lingering somewhere...</p>
  
  <p>Is this what's going on?
  How can I clean up the oauth token?</p>
  
  <p>I've tried several approaches, run at the PageReady of the login page (ie clean up all persisting logins when hitting the login page)</p>
  
  <pre><code>var user = UserManager.FindByName( User.Identity.Name );
  var AuthenticationManager = HttpContext.GetOwinContext().Authentication;
  
  AuthenticationManager.SignOut();
  AuthenticationManager.SignOut( DefaultAuthenticationTypes.ApplicationCookie );
  Session.Abandon();
  
  if ( user != null )
  {
      UserManager.UpdateSecurityStamp( user.Id ); // remove the old cookie so it cant' be reused to re-log in - EWB
  }
  </code></pre>
  
  <p>and finally </p>
  
  <pre><code>    return Redirect( "https://www.google.com/accounts/Logout?continue=https://appengine.google.com/_ah/logout?continue=https://"+ Url.Action( "Index", "Home", new { target = "_blank" } ) ); //https://stackoverflow.com/questions/27515518/asp-net-identity-external-login-wont-log-out - f belihocine answer
  </code></pre>
  
  <p>Which is supposed to be logging out of google (and goes to our custom logout page, so it seems to be true).</p>
  
  <p>but I'm still getting the same behavior</p>
  
  <p>What exactly is going on?</p>
  
  <p>If I wait till the timeout expires (10 min) things work normally... </p>