Make check for privileged container work with cgroup v2

[vincentbernat]

When running on top of a distribution using cgroup v2 (Debian
Bullseye, Fedora >= 31, Arch), creating a file at the base of the
hierarchy is not possible. However, we can create a directory.

[vincentbernat]

Note that I didn't test if it works with cgroup v1, but I think it does.

[BonZur]

Damn! You have no idea how much time I have wasted on this before I notice this info here, everyone is using old crap systems and never care to update !? WTH, Thanks Vincent

The problem is when direcotry is already created it will fail unless you reboot sys or append dir name creating another and another if you want to start another instances

[mmouselli]

I went through this and I can confirm this would fix it for Debian/Ubuntu22, Thank you Vincent!