gpg: Enhance agent_probe_secret_key to return bigger value.
* g10/call-agent.c (keyinfo_status_cb): Parse more fields. (agent_probe_secret_key): Use KEYINFO and returns bigger value representing the preference.
Backport the commit of:
8748c50bfaa8df2b1e59c301d15fd6b9ddbd9c47
- GnuPG-bug-id: T3456
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>