Make sure MaintenanceFixup's shutdown is simulated

Make sure MaintenanceFixup's shutdown is simulated

Previously, MaintenanceTest created a MaintenanceFixup in setUp and
relied on each test to call MaintenanceFixup's simulateShutdown instead
of making sure this was called in tearDown. Change Iee1261e7 broke this
by introducing a meta-test in a parent class.

Fixing that also allows us to not have to special-case failed tests.

Change-Id: I67c8615dd94734bb55ca48aac0c66298accbe0b4