supervisor doesn't always respond to TERM

[robnagler]

#7404 (review)

I can't create a reproducible example but this has happened to me 3 times: The supervisor can get in a state where it no longer responds to SIGTERM.

~$ ps uww | grep job_supervisor
vagrant   426434  6.5  2.0 596624 164596 pts/2   Sl+  16:41   0:32 /home/vagrant/.pyenv/versions/3.9.15/envs/py3/bin/python /home/vagrant/.pyenv/versions/py3/bin/sirepo job_supervisor
~$ kill -SIGTERM 426434
~$ ps uww | grep job_supervisor
vagrant   426434  6.5  2.0 596624 164596 pts/2   Sl+  16:41   0:33 /home/vagrant/.pyenv/versions/3.9.15/envs/py3/bin/python /home/vagrant/.pyenv/versions/py3/bin/sirepo job_supervisor

When I send the SIGTERM to the supervisor it logs

Jan 06 16:49:33 426434     0 sirepo/job_driver/local.py:87:kill LocalDriver(a=foCR k=sequential u=d2dF []) pid=427224

The closest I can get to a reproducible example is it seem to only happen when the supervisor is signaled while a job is running.