doc: Update Japanese lxc.conf(5)

Update for commit df2d4205073d3f57543951ca7ffabf891b230634

Signed-off-by: KATOH Yasufumi <karma@jazz.email.ne.jp>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
install only lxc-user-nic setuid

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>