cgroup2 detection is faulty

[haesbaert]

From /proc/mounts

cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0
^ we look here           ^ we should look here       

The first word is whatever is used in the first argument of mount, which for these filesystems can be "anything", for example:

mount("cgroup2", "/sys/fs/cgroup", "cgroup2", 0, NULL)
VS
mount(NULL, "/sys/fs/cgroup", "cgroup2", 0, NULL)

Are both valid, but the second will print "none" in the first word of /proc/mounts.

We should look at the third word, not the first.