w32: Also change the directory on daemon startup.

* agent/gpg-agent.c (main): Always to the chdir.
* dirmngr/dirmngr.c (main): Ditto.
* scd/scdaemon.c (main): Ditto.

Note that only dirmngr did not call the chdir with --no-detach. thus
we kept it this way.

Tested gpg-agent by checking the properties shown by procexp.

• Gnupg-bug-id: T2670
• Signed-off-by: Werner Koch <wk@gnupg.org>