agent: Fix cancellation handling for scdaemon.
* agent/call-scd.c (cancel_inquire): Remove. (agent_card_pksign, agent_card_pkdecrypt, agent_card_writekey) (agent_card_scd): Don't call cancel_inquire.
Since libassuan 2.1.0, cancellation command "CAN" is handled within
the library, by assuan_transact. So, cancel_inquire just caused
spurious "CAN" command to scdaemon which resulted an error.
- Signed-off-by: NIIBE Yutaka <email@example.com>