storaged: clarify vdo-monitoring is for legacy vdo

Author: jelly

pkg/storaged/client.js

@@ -1354,6 +1354,7 @@ function legacy_vdo_overlay() {
     function start() {
         let buf = "";
 
+        // legacy vdo monitoring (RHEL-8)
         return cockpit.spawn(["/bin/sh", "-c", "head -1 $(command -v vdo || echo /dev/null)"],
                              { err: "ignore" })
                 .then(function (shebang) {