Synology Webstation seems to need this

[arran4]

Not sure if it's just this though still testing.

What I'm expecting to see when I build the image:

What I get. (Same image, mango is running but doesn't get listed.)

[arran4]

Got it working. For anyone else looking the work around before this PR is merged. It was downloading the json file from synology for the container and adding:

      "service_portals" : [
      {
         "port" : "9000",
         "protocol" : "http"
      }
   ]

Then re-uploading it