coord ack errors

[rmarianski]

Errors during coord ack appeared in the latest tilequeue run. These two types appear releated.

Traceback (most recent call last): 
  File \"/usr/local/lib/python2.7/dist-packages/tilequeue/worker.py\", line 524, in __call__    queue_msg_handle, done = self.msg_tracker.done(coord_handle)
  File \"/usr/local/lib/python2.7/dist-packages/tilequeue/queue/message.py\", line 134, in done    coord_id_set.remove(coord_handle)
KeyError: 140703535926664

Traceback (most recent call last): 
  File \"/usr/local/lib/python2.7/dist-packages/tilequeue/worker.py\", line 524, in __call__    queue_msg_handle, done = self.msg_tracker.done(coord_handle)
  File \"/usr/local/lib/python2.7/dist-packages/tilequeue/queue/message.py\", line 133, in done    assert coord_id_set is not None
AssertionError