dom0: provide explicit config path to xl save
dom0: provide explicit config path to xl save

The default behaviour is to take it from /var/lib/xen, where files are created
with mode 600, so unable to read it as normal user.

marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin