assets: also use cache busting via query string in files imported from acs.js

Before this change, a client would require two versions of the same assets (with
and without randomVersionString), wasting resources and triggering all sorts of
hard to debug inconsistencies.

This change should have been part of 95fd5ce2a4 and completes it.

src/node/handler/PadMessageHandler.js

@@ -1076,6 +1076,7 @@ async function handleClientReady(client, message)
     var clientVars = {
       "skinName": settings.skinName,
       "skinVariants": settings.skinVariants,
+      "randomVersionString": settings.randomVersionString,
       "accountPrivs": {
           "maxRevisions": 100
       },