tools/hotplug/Linux/init.d: fix wrong path in xendomains init

Fixed wrong path in xendomains init that make it not working, introduced
in commit d8bad9df2544291a0fdc8e4d826b16f9f5394462 (tools/xendomains:
move to libexec and use a smaller init helper).

Signed-off-by: Fabio Fantoni <fabio.fantoni@m2r.biz>