bug #3216: xen4 reset executes reboot with ACPI

xen 4.2 lacks reset command and can not be implemented with the information provided to
the driver (lacks deployment file path). The driver is changed so it calls reboot with
-F parameters so it will send ACPI signal in case it is HVM and does not have PV drivers.
Merge remote-tracking branch 'origin/bug-3216'