tests: cloud: env vars: restart supervisor to speed up tests

[rcooke-warwick]

Tests can get stuck here for 15 to 20 minutes if the timings are unlucky. Forcing a supervisor restart ensures a clean slate and ensures that the variables are included as quickly as possible

Saves 15+ minutes in some cases

fix for recurring test issue discovered as part of https://balena.fibery.io/Inputs/Research/OS-testing-failures-and-issues-1147

Change-type: patch

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[flowzone-app]

Website deployed to CF Pages, 👀 preview link https://d063844e.balena-os.pages.dev

[klutchell]

@pipex @rcooke-warwick is the bad timing just related to the poll interval or is something else going on?

[rcooke-warwick]

EDIT: Ignore me

[pipex]

I don't have a ton of context, but from a quick glance at the linked research, the polling hypothesis makes sense to me. In the worst case, if the change takes place close to the end beginning of a polling interval, the supervisor would have to wait a full interval to get the updated data, meaning the test would also be waiting during that time.