cgfs: don't mount /sys/fs/cgroup readonly

/sys/fs/cgroup is just a size-limited tmpfs, and making it ro does
nothing to affect our ability alter mount settings of its subdirs.
OTOH making it ro can upset mountall in the container which tries
to remount it rw, which may be refused.

So just don't do it.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Christian Seiler <christian@iwakd.de>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
Revert "cgfs: don't mount /sys/fs/cgroup readonly"

This reverts commit 5cfc06fae750e7222f0839a48b152c4f9da1633c.
lxc-ls: Force running against containers without python

When using --nesting, we exec ourselves in the container context, if we
somehow need to dynamically-load modules from there, things break. So
make sure we pre-load everything we may need.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>