For "make integration", the tests are run inside a Docker/Podman
container. Problem is, if cgroup v2 is used, the in-container
/sys/fs/cgroup/cgroup.subtree_control is empty.
The added script, used as Docker entrypoint, moves the current process
into a sub-cgroup, and then adds all controllers in top-level
cgroup.subtree_control.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Kir Kolyshkin