allOf implies that all (both) schemas should be valid, but
    additionalProperties false wont allow it, since it become multually
    invalid. (You can validate only one or None)

  Just use $ref to expand the list, it end up with the expected outcome
   reducing complexity.

  Note: kvm wasn't using additionalProperties false but it was changed
   because it makes it future proof, in case we set it (we should set).