Display NOTIFICATIONS on assert failure
Display NOTIFICATIONS on assert failure

From time to time we have itermitent errors regarding the
fake_notifier.NOTIFICATIONS count.

This patch does two things to try to find out which notifications are
being fired unexpectedly:
- Make sure that fake_notifier is reset in cleanup regardless of
  exception raised by shutil.rmtree
- Display fake_notifier.NOTIFICATIONS whenever count assertion fails.

Related-Bug: #1412513
Change-Id: I07370636d8b30098dcb2a70ef1985c2f5aee81be

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