Fixed discrepancy between the subscores and the total score and added some tests

ORA-199

When a peer grade is submitted to ORA it records the 'score' and if the submission is marked as flagged and the peer grader did not provide any rubric scores, the rubric_scores are set to 0. This bug should only happen if the peer grade did not have any rubric_scores and its 'score' value was not 0.

Fixing this by score=0 when a submission is flagged or marked as unknown by peer grader and rubrics are not provided.