title: Task progress is not updated latest status on Celery+RabbitMQ
body: <p>I implemented progress feedback of long task with <a href="http://celery.readthedocs.org/en/latest/userguide/tasks.html#custom-states" rel="nofollow">custom states</a> on Celery + RabbitMQ result backend.</p>
  
  <p>But the caller can't retrive the latest progess status as I expected. In following code, <code>result.info['step']</code> <em>always</em> return <code>0</code>, and then the task will be finished with "result=42".</p>
  
  <pre><code># tasks.py -- celery worker
  from celery import Celery
  app = Celery('tasks', backend='amqp', broker='amqp://guest@localhost//')
  
  @app.task
  def long_task():
    for i in range(0, 10):
      timer.sleep(10)  # some work
      self.update_state(state='PROGRESS', meta={'step': i})
    return 42
  
  
  # caller.py
  from tasks import long_task
  result = long_task.delay()
  
  while not (result.successful() or result.failed()):
    try:
      result.get(timeout=1)
    except celery.exceptions.TimeoutError:
      if result.state == 'PROGRESS':
        print("progress={}".format(result.info['step']))
  print("result={}".format(result.get()))
  </code></pre>
  
  <p>Python 3.4.1 / Celery 3.1.17 / RabbitMQ 3.4.4</p>