test_upgrade_with_open_child_fds failing on trusty

[Andreas Hasenack]

https://ci.lscape.net/view/Landscape%20Client/job/landscape-client-test/label=trusty-client/251/testReport/

landscape.package.tests.test_releaseupgrader.ReleaseUpgraderTest.test_upgrade_with_open_child_fds:

_StringException: Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 588, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "/var/jenkins/workspace/landscape-client-test/label/trusty-client/landscape/package/tests/test_releaseupgrader.py", line 493, in cleanup
    self.assertFalse(os.path.exists(child_pid_filename))
  File "/usr/lib/python2.7/dist-packages/twisted/trial/_synctest.py", line 389, in assertFalse
    super(_Assertions, self).assertFalse(condition, msg)
  File "/usr/lib/python2.7/unittest/case.py", line 418, in assertFalse
    raise self.failureException(msg)
FailTest: True is not false

[Simon Poirier (simpoir)]

the intermittent failures of this test seems to indicate it will be resolved when this lands https://bugs.launchpad.net/landscape-client/+bug/1603425