CP-9795: Add required init scripts

Add some init scripts only required by XAPI.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
CP-9795: Use "service restart" rather than "service start"

The attach-static-vdis script runs on boot.  Some service managers
(like systemd), keep track of a service's state and so starting a
service which has already been started is a no-op.  Use the restart
verb instead start to prevent this and ensure that the script runs
as desired.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>