Add a test for locally hosted s3 files in the case that the file is not in the tracking table

Closes #3292273

Adds a file system check to the S3FileOriginLocator service to prevent requests to ContentHub for items stored within the site's own S3 storage when there is no tracking information in the S3 File Mapping table.

This will, in the case of name collisions, cause a site to prefer the locally available copy of a file, rather than the remote version.