agent: Fix homedir check wrt --disable-check-own-socket option.

* agent/gpg-agent.c (handle_connections): Don't disable use of inotify
when it has the --disable-check-own-socket option.

Before the fix, it checks the homedir using the gnupg_stat function
when --disable-check-own-socket is enabled, without trying use of
inotify.

• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>