In the case where either a question_attempt had not steps, or a
question_usage had not question_attempts, the load_from_records methods
could get stuck in an infinite loop.
This fix ensures that does not happen, with unit tests to verify it. At
the same time, I noticed an error in the existing tests, which this
patch fixes.
1/ type/match/tests/walkthrough_test.php - tests are failing randomly, looks like some weird randomisation is going on there - see TODOs
2/ type/multianswer/tests/upgradelibnewqe_test.php contains invalid expected value - see TODO
Tim Hunt