title: celery tasks with long eta (8+ hours) are executed multiple times in a row when eta is reached
body: <p>I'm creating a task with eta ranging between 3 and 20 hours and when I look at the worker log, for this task, the worker says "<code>Got task from broker: ...</code>" every hour after the original task was received until the eta is reached.</p>
  
  <p>I know that this has to do with setting <code>BROKER_TRANSPORT_OPTIONS = {'visibility_timeout': X}</code> where X is the number in seconds.</p>
  
  <p>So I played with the visibility_timeout and if I set it to anything less than 1 hour then I can see worker getting the same task every X seconds, however when I set the <code>visibility_timeout</code> to X being larger than 1 hour then it keeps defaulting to 1h regardless of the time I set.</p>
  
  <p>Does anyone else run into this issue? Is this a know bug?</p>
  
  <p>I'm using Celery 3.0.11 (Chiastic Slide)
  with Redis server version 2.4.15</p>