upgrades: migrate uploaded image metadata to environment storage

We no longer search for image metadata in provider storage.
This is the final piece: migrate existing metadata from provider
storage to environment storage, preserving paths and data exactly.
Merge pull request #797 from axw/upgrades-image-metadata

upgrades: migrate uploaded image metadata to environment storage

We no longer search for image metadata in provider storage.
This is the final piece: migrate existing metadata from provider
storage to environment storage, preserving paths and data exactly.