lxc-debian: adjust init system configurations

Do as much as possible to allow containers switching from non-systemd to
systemd to work as intended (but nothing that will cause side effects).
Use update-rc.d disable instead of remove so the init scripts are not
re-enabled when the package is updated

Signed-off-by: Cameron Norman <camerontnorman@gmail.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
lxc-debian: mask both Wheezy and Jessie udev services

Signed-off-by: Cameron Norman <camerontnorman@gmail.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>