lxccontainer: update locking comment

lxccontainer: update locking comment

Update the LOCKING comment.

Take mem_lock in want_daemonize.

convert lxcapi_destroy to not use privlock/slock by hand.

Fix a coverity-found potential dereference of NULL c->lxc_conf.

api_cgroup_get_item() and api_cgroup_set_item(): use disklock,
not memlock, since the values are set through the cgroup fs on
the running container.

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