Pinned snapshot pre release binaries use `-SNAPSHOT` operator image version

The pre release binaries coming from nightly build must not use `-SNAPSHOT` operator image versions when doing a `yaks install`

This leads to image pull errors as `-SNAPSHOT` image versions are obviously not released to dockerhub or quay.io

The pinned snapshot binaries must use `docker.io/yaks/yaks:` as operator image when doing a `yaks install`

Start by tracing the `yaks install` path for pinned snapshot binaries and how it selects the operator image version. Verify the change with a pinned pre-release binary and confirm the operator image is `docker.io/yaks/yaks:` without image pull errors.

Written by the indexing model from the issue text.