Comment 8 for bug 1584938

After discussing with Scott Moser, the problem seems to be that most of the metadata is not stored in glance, so if uploading a second image fails (for whatever reason), the metadata for the first one will be lost. Suggested solution is to store all the metadata in glance anyway (and we'll want to avoid raciness so will have to do that either before or at the same time as the image upload), and then always use that to regenerate the index file.