Increase timeout to avoid:

Traceback (most recent call last):
  File "/home/ubuntu/src/nodepool/nodepool/nodepool.py", line 457, in _run
    self.updateImage(session)
  File "/home/ubuntu/src/nodepool/nodepool/nodepool.py", line 530, in updateImage
    image_id = self.manager.createImage(server_id, hostname)
  File "/home/ubuntu/src/nodepool/nodepool/provider_manager.py", line 361, in createImage
    image_name=image_name))
  File "/home/ubuntu/src/nodepool/nodepool/provider_manager.py", line 251, in submitTask
    return task.wait()
  File "/home/ubuntu/src/nodepool/nodepool/task_manager.py", line 51, in run
    self.done(self.main(client))
  File "/home/ubuntu/src/nodepool/nodepool/provider_manager.py", line 166, in main
    return client.servers.create_image(**self.args)
  File "/usr/local/lib/python2.7/dist-packages/novaclient/v1_1/servers.py", line 773, in create_image
    resp = self._action('createImage', server, body)[0]
  File "/usr/local/lib/python2.7/dist-packages/novaclient/v1_1/servers.py", line 951, in _action
    return self.api.client.post(url, body=body)
  File "/usr/local/lib/python2.7/dist-packages/novaclient/client.py", line 232, in post
    return self._cs_request(url, 'POST', **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/novaclient/client.py", line 213, in _cs_request
    **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/novaclient/client.py", line 195, in _time_request
    resp, body = self.request(url, method, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/novaclient/client.py", line 189, in request
    raise exceptions.from_response(resp, body, url, method)
Conflict: Cannot 'createImage' while instance is in task_state powering-off (HTTP 409) (Request-ID: req-4f4b52a0-5179-465f-8fd5-f81e980a3a0e)