Command occ maintenance:mimetype:update-db --repair-filecache doesn't work

[AlexAndBear]

Steps to reproduce

1. Upload a file foo.bar
2. Copy resources/config/mimetypemapping.dist.json to config/mimetypemapping.json
3. Add the following entry to mimetypemapping.json:
   "bar": ["application/bar"]
4. Run php occ maintenance:mimetype:update-db --repair-filecache

Expected behaviour

The mimetype column in oc_filecache for the file foo.bar should be updated with the new mimetype foreignkey

Actual behaviour

1. New record application/bar will be created in oc_mimetypes
2. The mimetype column in the table oc_filecache for foo.bar won't be updated