New CI test failure in Melodic+

[mjcarroll]

'Unloading nodelet /test from manager nodelet_manager' not found in ''
  File "/usr/lib/python2.7/unittest/case.py", line 329, in run
    testMethod()
  File "/tmp/ws/src/nodelet_core/test_nodelet/test/test_bond_break_on_shutdown.py", line 57, in test_bond_break_on_shutdown
    self.assertIn('Unloading nodelet /test from manager nodelet_manager', n_out)
  File "/usr/lib/python2.7/unittest/case.py", line 804, in assertIn
    self.fail(self._formatMessage(msg, standardMsg))
  File "/usr/lib/python2.7/unittest/case.py", line 410, in fail
    raise self.failureException(msg)