🔩 Description: What code changed, and why?

Adding the initial unknown desktop control to the desktop skeleton page.

⛓️ Related Resources

#3220

👟 How to Build and Test the Change

1. start_all_services and start the UI
2. Add ten nodes chef_load_nodes 10
3. Back date checkin date of the nodes with the below.
   curl -X POST "$ELASTICSEARCH_URL/node-state/_update_by_query?pretty" -H 'Content-Type: application/json' -d'
   {
   "script": {
   "source": "ctx._source[\u0027checkin\u0027] = \u00272020-02-15T02:43:43Z\u0027",
   "lang": "painless"
   }
   }
   '
4. Open https://a2-dev.test/dashboards/desktop and look for the "Unknown Duration" control with 10 uknown desktop for each duration.

✅ Checklist

• I have read the CONTRIBUTING document.
• Tests added/updated?
• Docs added/updated?
• All commits have been signed-off for the Developer Certification of Origin.

📷 Screenshots, if applicable