sm: Fix agent communication.
* sm/call-agent.c (gpgsm_agent_pksign): Fix passing the control handle to the callback. (gpgsm_scd_pksign): Likewise. (gpgsm_agent_reaedkey): Likewise.
- GnuPG-bug-id: T2874
- Signed-off-by: Justus Winter <justus@g10code.com>