Fix issue with update train list

William added support for train redirection.  I tested with an internal build using internal update server.

First I created /data/update.conf with this

{
        "freenas-11.3-internal": {
                "redirect": "FreeNAS-11-Nightlies"
        }
}

After running the middlware call below I can confirm FreeNAS-11-Nighlies is the selected train.

midclt call update.get_trains|jq .

{
  "trains": {
    "FreeNAS-11-Nightlies": {
      "description": "Nightly builds for FreeNAS 11.  Very unstable, even ISO installs are not guaranteed to work. [nightly]",
      "sequence": null
    },
    "FreeNAS-11-Nightlies-SDK": {
      "description": "Nightly SDK builds for FreeNAS 11.  Very unstable, even ISO installs are not guaranteed to work. [nightly]",
      "sequence": null
    },
    "FreeNAS-11-STABLE": {
      "description": "Release Train for FreeNAS 11.1 [release]",
      "sequence": null
    },
    "FreeNAS-11.2-STABLE": {
      "description": "Release Train for FreeNAS 11.2 [release]",
      "sequence": null
    }
  },
  "current": "freenas-11.3-internal",
  "selected": "FreeNAS-11-Nightlies"
}

However the UI does now show any train selected as presented in the screenshot