cms/cmssetup.sh: understand DASD="none"

Treat DASD="none" as unset.

https://bugzilla.redhat.com/show_bug.cgi?id=1096979

modules.d/80cms/cmssetup.sh

@@ -173,7 +173,7 @@ processcmsfile()
         znet_cio_free
     fi
 
-    if [[ $DASD ]]; then
+    if [[ $DASD ]] && [[ $DASD != "none" ]]; then
         echo $DASD | normalize_dasd_arg > /etc/dasd.conf
         echo "options dasd_mod dasd=$DASD" > /etc/modprobe.d/dasd_mod.conf
         dasd_cio_free