Adapt automated test suite for the "one single SquashFS diff" upgrade scheme
We need scenarios for installing an IUK when:
- no IUK is present
- one IUK is present (make sure old one was removed)
- more than one IUK is present (make sure old ones were removed)
Feature Branch: feature/15281-single-squashfs-diff
Parent Task: #15281
Related issues
Original created by @anonym on 15286 (Redmine)