Ensure all devices under /dev show up with proper ownership

Inside a Sysbox container, some devices show up with nobody:nogroup ownership:

/ # ls -l /dev | grep nobody
crw-rw-rw-    1 nobody   nobody      1,   7 Oct 10 01:13 full
crw-rw-rw-    1 nobody   nobody      1,   3 Oct 10 01:13 kmsg
drwxrwxrwt    2 root     nobody          40 Oct 10 02:11 mqueue
crw-rw-rw-    1 nobody   nobody      1,   3 Oct 10 01:13 null
crw-rw-rw-    1 nobody   nobody      1,   8 Oct 10 01:13 random
crw-rw-rw-    1 nobody   nobody      5,   0 Oct 10 02:41 tty
crw-rw-rw-    1 nobody   nobody      1,   9 Oct 10 01:13 urandom
crw-rw-rw-    1 nobody   nobody      1,   5 Oct 10 01:13 zero

This is not ideal and sometimes causes problems (e.g., issue #839 ).

Ideally all these devices would show up with root:root ownership, as they would on a real host.

This likely requires that Sysbox intercept the mknod system call inside the container, as otherwise this syscall is blocked within the Sysbox container's user namespace.