The task hash stores a queue_name field that no reader uses #79

Found while reviewing PR #69 with the SuperJoe crew. Filed as out-of-scope there.

RedisTaskBackend.enqueue() stores queue_name in the task hash. No reader uses it. The acquire and mover scripts read data and score. The reaper only makes sure that the hash exists. Every reader takes the queue from task.queue_name in the payload or from the key that holds the id. The backend writes this field on each enqueue, but no code reads it.

Remove the field, or make one reader use it. Then the payload does not need to carry the queue name as well.

Reference: threadmill/backends/redis.py, the enqueue hash mapping.