s3: smbd: Add IS_VETO_PATH check to openat_pathref_dirfsp_nosymlink().

s3: smbd: Add IS_VETO_PATH check to openat_pathref_dirfsp_nosymlink().

Returns NT_STATUS_OBJECT_PATH_NOT_FOUND for directory component.
Note IS_VETO_PATH only looks at the last component, so we must
do it during the directory walk on each component.

Note, we also have to check after a call to get_real_filename_at()
as it may have demangled the client sent name into a filesystem
name that matches the "veto files" parameter.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15143

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>