fix #4001: ui: add prefix to files downloaded through the pxar browser

Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

www/datastore/Content.js

@@ -768,8 +768,9 @@ Ext.define('PBS.DataStoreContent', {
 		title: `${type}/${id}/${timetext}`,
 		listURL: `/api2/json/admin/datastore/${view.datastore}/catalog`,
 		downloadURL: `/api2/json/admin/datastore/${view.datastore}/pxar-file-download`,
-		enableTar: true,
 		extraParams,
+		enableTar: true,
+		downloadPrefix: `${type}-${id}-`,
 		archive: rec.data.filename,
 	    }).show();
 	},