assess_network_health KeyError dns

[Curtis Hovey]

As seen at
     http://reports.vapour.ws/releases/issue/55a87d78749a560d3358394e

The assess_network_health test presumes the dns key always exists in status.

2017-03-20 15:13:08 INFO Starting network tests.
2017-03-20 15:13:14 ERROR 'dns'
Traceback (most recent call last):
  File "/mnt/jenkins/juju-ci-tools/utility.py", line 426, in logged_exception
    yield
  File "/mnt/jenkins/juju-ci-tools/deploy_stack.py", line 897, in runtime_context
    yield
  File "/mnt/jenkins/juju-ci-tools/deploy_stack.py", line 1007, in booted_context
    yield machines
  File "/var/lib/jenkins/juju-aci-tools/assess_network_health.py", line 586, in main
    maas=manager)
  File "/var/lib/jenkins/juju-ci-tools/assess_network_health.py", line 66, in assess_network_health
    results_pre = self.testing_iterations(client, series, target_model)
  File "/var/lib/jenkins/juju-ci-tools/assess_network_health.py", line 91, in testing_iterations
    interface_info = self.get_unit_info(client)
  File "/var/lib/jenkins/juju-ci-tools/assess_network_health.py", line 221, in get_unit_info
    results[machine]['dns'] = out['results']['dns']
KeyError: 'dns'

The test may need to wait for the dns key to exist.

[Aaron Bentley (abentley)]

The failing code was removed in r1939, but this code has not been applied to the slaves for some reason.