rpcclient: use json_encode_binary for verbose output
    
    `json.dumps` is not able to process some IPA's object types and therefore requires to preprocess it with `json_encode_binary` call. This step was not used in  rpcclient's verbose output.
    
    https://fedorahosted.org/freeipa/ticket/4773
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>