TA Grading Race Condition when moving to next student and/or next rubric item

[bmcutler]

Describe the bug When grading a large group of students using the TA grading system, we have occasional errors where the grading fails to save. It may happen more often when lots of graders are working at the same time (e.g., everyone working at the same time to grade an exam).

It happens when a rubric component is open, and then the right(or left) arrow key is used to move to the next (or previous) student. It is SUPPOSED to save the open component, go to the next student, and open that same component for the next student.

It may also happen when a rubric component is open, and the down (or up) arrow key is used to move to the next (or previous) component on the same student.

The problem is that after grading a a section of students, the grader looks back and some of the students are missing scores -- the grader remembers scoring them and filling out marks, but those edits are lost.

If the save button is explicitly pressed to close and save each component, everything seems to save correctly.
but this requires more clicks to save and reopen components and is slower.

I think this is related to the speedup we made several months ago. #10383 #10406