MDL-14471 - when attempt data is generated by a script then sometimes quiz_get_latest...

MDL-14471 - when attempt data is generated by a script then sometimes quiz_get_latest_attempt_by_user fetches the wrong attempt since timestart for the attempt is not a second apart from the last attempt - "patch to quiz/locallib.php function quiz_get_latest_attempt_by_user which makes the query simpler and also makes it more robust.

In the case that there are two attempts started in the same second, which can happen if you are generating random attempt data then the id field is used to tell which is the later attempt."