This reverts commit 7bca1c9b.

As it turns out it's not a good idea on systemd hosts.  The root
cgroup can have all controllers enabled but they don't have to be
enabled for sub-cgroups.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>