Fail tests which leave unfinished transitions behind

If a test starts a transition without finishing it, it will
cause subsequent tests to fail (sometimes passing itself still).

To help identify which tests cause this, add a check to teardown.

Bug: 183993924
Test: any subclass
Change-Id: Ib240a0c073c2e4eee4241735f0d91331702a6594
1 file changed