Partially equivalent to commit abf5ef6c22 ("apparmor: Allow pasta
to remount /proc, access entries under its own copy"): we should
allow pasta to remount /proc. It still works otherwise, but further
UID remapping in nested user namespaces (e.g. pasta in pasta) won't.
Reported-by: Laurent Jacquot <jk@lutty.net>
Link: https://bugs.passt.top/show_bug.cgi?id=79#c3
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>