ws2_32: Pass completion routing to NtDeviceIoControlFile in server_ioctl_sock only if caller provided completion routine.

Otherwise we're always doing non-blocking calls, preventing server from
doing the right thing (and in actually doing the opposite in
WS_SIO_ADDRESS_LIST_CHANGE case).
Signed-off-by: Jacek Caban <jacek@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>