LICENSES: Add note to CDDL-1.0 license that it should not be used

The only reason we have the CDDL-1.0 license text around is for some
dual-licensed files from virtualbox. New code should not use this license.

Add a note about this and change the example tag to be dual-licensed.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>