py3: decode bytes for json.loads()
    
    In py 3.5 json.loads requires to have string as input, all bytes must be
    decoded.
    
    Note: python 3.6 supports bytes for json.loads()
    
    https://fedorahosted.org/freeipa/ticket/4985
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>