With blockdev we can use the full range of commands to manipulate the
tray and the medium separately. Implement monitor code for this.

Schema testing done in the qemumonitorjsontest allows us to verify that
we generate the commands correctly.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>