s3-spoolss: fix spoolss GetPrinterData behaviour

s3-spoolss: fix spoolss GetPrinterData behaviour

Windows sends spoolss GetPrinterData requests with an offered buffer
size of zero, Model and TrayFormTable data is commonly requested in
this way.

Samba's GetPrinterData response for the above case includes the correct
error code (WERR_MORE_DATA), however the type field is set to REG_NONE.
This causes Windows (seen on XP and 2k3) to give up on the request.

If the type field is retained (not set to REG_NONE) when responding with
WERR_MORE_DATA, Windows reissues the GetPrinterData request with an
increased offered buffer size.

Signed-off-by: Günther Deschner <gd@samba.org>