py3: softhsm key_id must be bytes
    
    softhsm works with bytes, so key_id must be byte otherwise we get errors
    from bytes and string comparison
    
    https://fedorahosted.org/freeipa/ticket/4985
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>