xen/pvshim: set correct domid value

xen/pvshim: set correct domid value

If domid is not provided by L0 set domid to 1 by default. Note that L0
not provinding the domid can cause trouble if the guest tries to use
it's domid instead of DOMID_SELF when performing hypercalls that are
forwarded to the L0 hypervisor.

Since the domain created is no longer the hardware domain add a hook
to the domain shutdown path in order to forward shutdown operations to
the L0 hypervisor.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>