UI shows loading screen for entire install while doing fully automated install

[Dan Bungert]

While testing build 20240422 of noble-desktop daily-live with a fully-automated install, I observed that the loading screen never moved on from "Preparing Ubuntu".

The install did complete successfully otherwise. During the install I observed that /meta/status was returning a RUNNING state.

[Dan Bungert (dbungert)]

A second install produced the same result. The first two installs used refresh-installer: {update: yes}.
A third install used refresh-installer: {update: no} and behave correctly.

Dennis observed the following:
> in subiquity-server-debug.log.3845 from your logs I see
> 2024-04-22 14:41:41,983 INFO root:38 start: subiquity/Meta/status_GET:
> which is not followed by a subiquity/Meta/status_GET: SUCCESS: 200 ...
> possibly what causes the broken state in the UI

[Dan Bungert (dbungert)]

I believe that Subiquity-side, on shutdown of the server process, the outstanding waiting API calls are returning null. This is outside the API contract of /meta/status, which claims to only return ApplicationStatus.