Uncaught exception when Deckhand call fails

[sh8121att]

2018-03-26 22:04:42,080 - ERROR - orchestrator.py:_collect_subtask_futures - Uncaught excetion in subtask b43bffff-562a-4206-8cde-b0120cbac333 future:
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "./drydock_provisioner/orchestrator/actions/orchestrator.py", line 459, in start
    target_nodes = self.orchestrator.get_target_nodes(self.task)
  File "./drydock_provisioner/orchestrator/orchestrator.py", line 330, in get_target_nodes
    if design_status.status != hd_fields.ActionResult.Success:
AttributeError: 'NoneType' object has no attribute 'status'

[sh8121att]

This is related to #80