Stop AJAX when success or failure and show form on failure

AJAX requests stop on success or failure, as the waiting page
does not have to referesh any longer.

Also on failure a form that allows user to try again
is shown.

app/assets/javascripts/updateContent.js

@@ -28,7 +28,12 @@
         'data': form ? $('#' + form).serialize() : {}
       }
     ).done(
-      response => flushQueue(queue, response)
+      response => {
+        flushQueue(queue, response);
+        if (response.stop === 1) {
+          poll = function(){};
+        }
+      }
     ).fail(
       () => poll = function(){}
     );