30-tune-worker-processes.sh: cgroups2 workaround

cgroups2 may be set in weird way:

<<<
  $ podman run --rm --network=host debian:stable-slim sh -c 'grep cgroup /proc/self/mountinfo ; echo ; cat /proc/self/cgroup'
  754 752 0:27 /../../../../../.. /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - cgroup2 cgroup2 rw,nsdelegate,memory_recursiveprot

  0::/
>>>

add workaround for that case

Signed-off-by: Konstantin Demin <rockdrilla@gmail.com>