Extend file delete of local files to files which might have wrong location metadata

[djarran]

Description: Implement similar task as in Moodle's ObjectFS to reconcile files on disk

Issue: catalyst/moodle-tool_objectfs#588
PR: catalyst/moodle-tool_objectfs#724

As noted in the PR, this would:

1. if the hash exists on disk, but not in the database then we should be safe to just delete the file
2. if the hash exists on disk and in mdl_files but no in objectfs then we add it with the metadata as local