Fix the size up-down control becoming smaller every time the apply button is pressed in the Desktop
Integration tab.

UDM_SETBUDDY always shrinks the buddy window for a up-down control according to tests. And a
PSN_SETACTIVE notification is sent every time the apply button is pressed, thus init_dialog() gets
called again and sends an extra UDM_SETBUDDY message.
Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>