dom0/hvm-config: add parameters for DHCP server in stubdom

This cannot be done via xenstore, because stubdom is started just after
creating (unlike real VM, which is created paused), so there is no time for
creating xenstore entries.

dom0/misc/vm-template-hvm.conf

@@ -31,3 +31,6 @@ vcpus = {vcpus}
 on_poweroff = 'destroy'
 on_reboot   = 'destroy'
 on_crash    = 'destroy'
+
+# Use of DNS2 as DHCP server IP makes DNS2 not accessible, but DNS1 still should work
+device_model_args = [ '-net', 'lwip,client_ip={ip},server_ip={dns2},dns={dns1},gw={gateway},netmask={netmask}' ]