update does not update database entries

[LinearParadox]

For example, using gb.update_or_add_submission(assignment, student, **kwargs) will succesfully add a submission if it isn't there. However, it will not actually update a submission if it is already present. For example, trying to modify a score with gb.update_or_add_submission(assignment, student, score=num) will not modify the database.

[brichet]

@LinearParadox is this issue still there in latest version ?