[libcontainer] GetOwnCgroup is currently not supported for cgroup v2

[h-vetinari]

Opening an issue mentioned by @giuseppe here. Feel free to edit this OP.

[kolyshkin]

The implementation seem to be something like

func GetOwnCgroupV2() (string, error) {
  if !IsCgroup2UnifiedMode() {
    return errors.New("not implemented for cgroup v1")
  }
  out, err := ioutils.ReadFile("/proc/self/cgroup")
  if err != nil {
    return "", err
  }
  return strings.TrimPrefix("0::", out), nil
}

Or did you have something different in mind @giuseppe? Also, what is the use case?