Using rake script to fix exsiting grading errors

We need to fix course Hai Siang and Yanjie's course using this script.

If a course is using TOZ grader, the script will re grade all the training submission mcq questions and update the grade.

Usage:
Fix course 99:
rake training: re_grading_mcq[99]
this is unnecessary since you only call mcq_grader when there is a grading, just pass it in.