compute server: stopping a large number of compute servers at once associated to a course doesn't robustly work if Automatically Restart is enabled for them

[williamstein]

1. Set this for the instructor compute server:
2. Create a course with about 20 students and servers
3. Start them all
4. Click the checkbox, then "Stop" them all.

I have personally observed this, but there was a report from a user that some of the servers autorestarted again after stopping via the above method. This is surely caused by the temporary disabling of autorestart not working properly for them.

WORKAROUND: Stop the servers in smaller batches.