add autoredirect auth config

It redirects the user to to the Host header's domain whenever they try to use
token auth.

Signed-off-by: David Wu <david.wu@docker.com>

registry/handlers/app.go

@@ -847,7 +847,7 @@ func (app *App) authorized(w http.ResponseWriter, r *http.Request, context *Cont
 		switch err := err.(type) {
 		case auth.Challenge:
 			// Add the appropriate WWW-Auth header
-			err.SetHeaders(w)
+			err.SetHeaders(r, w)
 
 			if err := errcode.ServeJSON(w, errcode.ErrorCodeUnauthorized.WithDetail(accessRecords)); err != nil {
 				dcontext.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)