* tools/card-call-scd.c (start_agent): Request serialno only whean
started.
(scd_serialno): Allow NULL for r_serialno.
* tools/gpg-card.c (cmd_factoryreset): Use changed scd_serialno.
(cmd_list): New.
(dispatch_command): Use cmd_list for cmdLIST.
(interactive_loop): Ditto.