produce cloud image in vmdk format
    
    This is needed for uploading the image to aws using the
    github.com/coreos/mantle code base. We can upload the raw
    files but it is a significant waste of bandwidth to do so.
    
    Right now aws import-image does not support qcow2 files,
    otherwise we would be using that.
    
    Signed-off-by: Dusty Mabe <dusty@dustymabe.com>