cloud base: drop making vmdk image for now until we have a updated productmd that supports it.
    
    Without productmd support, it causes the compose to fail due to invalid
    type. See: https://pagure.io/dusty/failed-composes/issue/1574
    Also, see:
    https://github.com/release-engineering/productmd/pull/108/commits/7ebc4652be1c1045d750f92d7cccc358f647a4e1
    
    Signed-off-by: Kevin Fenzi <kevin@scrye.com>