tests: hup: login with sdk before fetching image

[rcooke-warwick]

This is to ensure we have an authenticated SDK before trying to get the last known production image - it needs to be authenticated in case the DT is private, otherwise it won't be able to fetch anything

Change-type: patch

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[rcooke-warwick]

marking as draft until I've locally tested this as nothing private is tested in the PRs

[rcooke-warwick]

I tested this with a private device type locally, and it did work