like lxc-ps and lxc-ls, lxc-netstat breaks if there is not an 'lxc' cgroup
mount and /etc/mtab is not a link to /proc/mounts.
Author: Serge Hallyn <serge.hallyn@canonical.com>
Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/819319
Forwarded: no
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>