Fix up the ora2 scores affected by the track changes bug.

  For affected assessments:
    - Sets PeerWorkflowItem.scored = 0 if currently = 1
    - Recalculates the score for the submission
    - If new score > old score, update the Score.points_earned with the new score
What exactly do you mean? You've just set the item to have PeerWorkflowItem.score = 0, and now you say in this comment that things with score == 0 won't be considered? So doesn't that mean that we won't be doing any regrading at all?