doc: Update lxc.conf(5)

* Update Japanese lxc.conf(5) for commit 508c263ee6ed2fac73f6979af287caba38963b4b
* Remove duplicate line in English lxc.conf(5)

Signed-off-by: KATOH Yasufumi <karma@jazz.email.ne.jp>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>