gpg: Fix just changed agent_get_s2k_count.

* g10/call-agent.c (agent_get_s2k_count): Actually return the count.

The previous push was definitely a bit to hasty.

• Fixes-Commit: ec13b1c562e34c0fcbc7b848ab6dc187b79cf2c1
• Signed-off-by: Werner Koch <wk@gnupg.org>