add patches for cgroup handling in non-unified cgroup setups

add patches for cgroup handling in non-unified cgroup setups

I opened a PR at lxc-upstream with these changes [0].

Testing in my hybrid layout environment fixes the issue with
priviledged container reported in the forum.
(Note that the issue also occurs with unprivileged container, if they
have a `lxc.cgroup.devices.(allow|deny)` entry (which they don't in
our default config)

[0] https://github.com/lxc/lxc/pull/3911

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>