s3: fix fallback owner lookup to use specific version
Address review feedback: the fallback logic was incorrectly using
getLatestObjectVersion which returns the wrong owner when different
versions have different owners.
Fix by using getSpecificObjectVersion with the version.VersionId to
fetch the correct entry for the specific version being processed.
This also simplifies the code by removing the separate null version
handling since getSpecificObjectVersion already handles that case.
Chris Lu
697b56003d