Fail a test if time.sleep called for no reason

If a mild error screws something up in task manager, an entire class
of tests will continue polling using GET requests until they hit their
rate limit, destroying any attempt to parse the test output to see
what is wrong. This pull request fixes that.

Change-Id: I7c00a174dfb7970357ee2bd71550983d68e0e8ae
Closes-Bug: 1315518
Merge "Fail a test if time.sleep called for no reason"