Fix Jobs not using addional labels

What does this MR do?

Fix Jobs not using addional labels

The selfsigned, the issuer and the upgrade check Jobs did not use additonal global labels.

Fixed by using the common helper functions for labels.

Closes #5903 (closed)

Changelog: fixed

This algins with our usage in other Jobs, e.g. the migrations Job.

Related issues

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Closes #5903 (closed)