batch command can be used to trigger internal errors on server
    
    In ipalib, the batch command expects a specific format for arguments.
    The code did not check the format of the parameters, which could trigger
    internal errors on the server.
    With this fix:
    - a ConversionError is raised if the arg passed to batch() is not a list of
    dict
    - the result appended to the batch results is a ConversionError if the
    'params' does not contain a tuple(list,dict)
    
    https://fedorahosted.org/freeipa/ticket/5810
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>