"lxc.cgroup.dir" can be used to set the name of the directory the container's
cgroup will be created in. For example, setting

    lxc.uts.name = c1
    lxc.cgroup.dir = lxd

would make liblxc create the cgroup

    lxd/c1
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>