smbd: Fix DELETE_ON_CLOSE behaviour on files with READ_ONLY attribute

smbd: Fix DELETE_ON_CLOSE behaviour on files with READ_ONLY attribute

MS-FSA states that a CREATE with FILE_DELETE_ON_CLOSE on an existing
file with READ_ONLY attribute has to return STATUS_CANNOT_DELETE. This
was missing in smbd as the check used the DOS attributes from the CREATE
instead of the DOS attributes on the existing file.

We need to handle the new file and existing file cases separately.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13673

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>