quiz_get_user_attempts() does not return result in a deterministic order.

MDL-41922 introduced the ability for quiz_get_user_attempts() to handle more than 1 quiz. It added a unit test that handled multiple quizzes.

That test assumes that the results of quizzes will be in a certain order. They are sorted by attempt. However with multiple quizzes, there are multiple attempt 1's and you can get either quiz first. In MySQL you will always get the same order, but in PostgreSQL that in not guaranteed and results in random unit test failures. The result may not make sense when sorted in that order either.