When "lxc.autodev = 1", LXC creates automatically a "/dev/.lxc/<name>.<hash>"
folder to put container's devices in so that they are visible from both
the host and the container itself.

On container exit (ne it normal or not), this folder was not cleaned
which made "/dev" folder grow continuously.

We fix this by adding a new `int lxc_delete_autodev(struct lxc_handler
*handler)` called from `static void lxc_fini(const char *name, struct
lxc_handler *handler)`.
Signed-off-by: Jean-Tiare LE BIGOT <jean-tiare.le-bigot@ovh.net>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>