Image purge needs to support airgapped environments

[Martin-Weiss]

Seems that this can not work in airgapped environments - so can we get this "fixed" so it works in airgapped environments as well?

https://github.com/harvester/upgrade-helpers/blame/90645ef71c8747acf643bd20a6b87eb02b202e4e/bin/harv-purge-images.sh#L35

[simonflood]

Theoretically it should be possible to amend the script to point to local copies of the required image-lists.tar.gz files. Unfortunately not all files are available - I've just logged #12 as files missing for v1.0.x and v1.3.x.