Make resolve_commit not set published property
    
    A ContainerImage published property is resolved and set by
    resolve_published. Therefore, if resolve_commit sets the published
    property, there will be a side-effect when resolve_commit is called
    again against an already resolved image, that is published property is
    reset to None.
    
    Whatever a ContainerImage is published or not, resolve_published will
    always set the property. So, just simply remove ``published`` from
    return value of _get_default_additional_data().
    
    Resolves: FACTORY-6028
    
    Signed-off-by: Chenxiong Qi <cqi@redhat.com>