If DeletePrinterDriverEx is called with DPD_DELETE_ALL_FILES and files
assigned to the to-be-deleted driver overlap with other drivers then an
error is returned. Change the error code here to match Windows 2k8r2.
Signed-off-by: David Disseldorp <ddiss@samba.org> Signed-off-by: Andreas Schneider <asn@samba.org>