title: Celery tasks don't get revoked
body: <p>I'm running multiple simulations as tasks through celery (version 2.3.2) from django. The simulations get set up by another task:</p>
  
  <p>In views.py:</p>
  
  <pre><code>result = setup_simulations.delay(parameters)
  request.session['sim'] = result.task_id # Store main task id
  </code></pre>
  
  <p>In tasks.py:</p>
  
  <pre><code>@task(priority=1)
  def setup_simulations(parameters):
      task_ids = []
      for i in range(number_of_simulations):
          result = run_simulation.delay(other_parameters)
          task_ids.append(result.task_id)
      return task_ids
  </code></pre>
  
  <p>After the initial task (setup_simulations) has finished, I try to revoke the simulation tasks as follows:</p>
  
  <pre><code>main_task_id = request.session['sim']
  main_result = AsyncResult(main_task_id)
  # Revoke sub tasks
  from celery.task.control import revoke
  for sub_task_id in main_result.get():
      sub_result = AsyncResult(sub_task_id); sub_result.revoke() # Does not work
      # revoke(sub_task_id) # Does not work neither
  </code></pre>
  
  <p>When I look at the output from "python manage.py celeryd -l info", the tasks get executed as if nothing had happened. Any ideas somebody what could have gone wrong?</p>