agent: Send back all public keys for available cards.
* agent/call-scd.c (card_cardlist_cb, agent_card_cardlist): New. * agent/command-ssh.c (card_key_list): New. (ssh_handler_request_identities): Call card_key_list and loop for the list to send public keys for all available cards.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>