Check that jobs will run OK on all LRM also when USE_PROCESS_GROUPS is set
GLIDEIN_Use_PGroups (setting USE_PROCESS_GROUPS) are set to True when using singularity to allow secure CVMFS (see [#17662]).
There is a warning from the HTCondor team about potential problems:
"""Imagine HTCondor is running under another batch system, and this batch system relies on process sessions created by calls to setsid() to kill the job. For example, imagine PBS is implemented to create a new process session when starting a job, and that when it wants to kill a job it sends signal SIGKILL (9) to all processes in the session. If HTCondor is configured to start a new session for the job, the result is PBS would send a signal 9 to all the HTCondor daemons but not to the HTCondor job itself, resulting in the job being "leaked".
Note I have no idea if PBS behaves this way or not, just using it as potential example."""
We want to verify that this problem is not present.
The task is to ser GLIDEIN_Use_PGroups to True and verify that there are no processes leftover on all supported LRMs (batch systems)