Fix preferred apps order for multiple level mime inheritance

We should prefer more specific mime types to less specific for that reason offers are sorted by inheritance level first. When constructing the offers for inherited types, the associated services for parent types are queried. However these can already contain services that are associated with a parent type of the parent type as the offers are build from the bottom-up starting with the least specific mime type. For example when constructing offers for a mime-type that inherits text/plain, the returned offers for text/plain will already contain services associated with application/octet-stream. By incrementing the inheritance levels instead of overwriting the relative ordering of inherited mime types is preserved. BUG:475200