os-image-server not always serving up-to-date image

( This issue is a "fork" of #1860 (closed), following up to this comment, for the specific case of checksum error which is due to an os-image-server bug)

For a given os/flavor, for different versions of diskimage-builder (0.4.3 and 0.3.11) used by consecutive versions of sylva, we sometimes have the same k8s-version and hence the same filename in the OCI artifact (e.g. opensuse-15-6-hardened-rke2-1-30-9).

In such a case, when os-image-server is updated during a Sylva upgrade, it will get all the new information for the new image, but since the filename hasn't changed (and because the PV name is also the name, it's taken from the sylva_diskimagebuilder_images key), it will conclude that it does not need to download it again, and will keep the old one (code here).