when running in rootless mode and using systemd as cgroup manager
create automatically a systemd scope when the user doesn't own the
current cgroup.
This solves a couple of issues:
on cgroup v2 it is necessary that a process before it can moved to a
different cgroup tree must be in a directory owned by the unprivileged
user. This is not always true, e.g. when creating a session with su
-l.
Closes: https://github.com/containers/libpod/issues/3937
Also, for running systemd in a container it was before necessary to
specify "systemd-run --scope --user podman ...", now this is done
automatically as part of this PR.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>