agent: Change intialization of assuan socket system hooks.
* agent/gpg-agent.c (initialize_modules): Add hook again. (main): Remove setting of the system houk but add scoket system hook setting after assuan initialization.
Thread initialization is better to be deferred after fork (in case of
UNIX). assuan_sock_init should be earlier. Thus, we need to change
system hooks for assuan_sock_* interface. Or else, on Windows, it may
cause hang on server.
- GnuPG-bug-id: T3378
- Signed-off-by: Werner Koch <firstname.lastname@example.org>