Specify cgroup mount options explicitly to exclude the net_prio option,
which cause an error when a subdirectory is created.
Add cgroup devices for lxc.
Use lxc-wait to wait for lxc containers to shutdown in lxc-auto.
Use lxc version 0.9.0 instead of 0.7.5.
Remove unused code for lxc version 0.7.5.