Slurm does not clean cgroupv2

[rezib]

For an unknown reason, Slurm does not properly clean cgroupv2 hierarchy and it ends up being full and fail with no space left in cgroup virtual filesystem.

A workaround is to clean empty cgroups on compute nodes, with:

On Debian:

# clush -bw cn[1-4] 'find /sys/fs/cgroup/system.slice/cn?_slurmstepd.scope -depth -type d -exec rmdir {} +'

On Rocky:

$ clush -bw cn[1-4] 'find /sys/fs/cgroup/system.slice/slurmstepd.scope -depth -type d -exec rmdir {} +