set the correct X-Forwarded-Port header to fix SAML auth

see: https://github.com/ansible/tower/issues/2314

installer/roles/image_build/files/nginx.conf

@@ -77,6 +77,7 @@ http {
             uwsgi_read_timeout 120s;
             uwsgi_pass uwsgi;
             include /etc/nginx/uwsgi_params;
+            proxy_set_header X-Forwarded-Port 443;
         }
     }
 }