[archiso] Update nbd hook to match newer nbd operation mode.

Newer nbd-server uses config file instead of parameters via cmd line (deprecated).
Also does not use a fixed port (oldstyle).

Sample nbd-server.conf that works with this change:

-- CUT HERE --
[generic]
[archiso]
    readonly = true
    exportname = /tmp/archlinux.iso
-- CUT HERE --

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

archiso/hooks/archiso_pxe_nbd

@@ -68,11 +68,11 @@ archiso_pxe_nbd_mount_handler () {
         sleep 1
     done
 
-    msg "::: Setup NBD from ${nbdserver}:9040 at /dev/nbd0"
+    msg "::: Setup NBD from ${nbdserver} at /dev/nbd0"
     if [ "${copytoram}" = "y" ]; then
-        nbd-client ${nbdserver} 9040 /dev/nbd0
+        nbd-client ${nbdserver} -N archiso /dev/nbd0
     else
-        nbd-client ${nbdserver} 9040 /dev/nbd0 -persist
+        nbd-client ${nbdserver} -N archiso /dev/nbd0 -persist
     fi
 
     archisodevice=/dev/nbd0