s3: smbd. Generic fix for incorrect reporting of stream dos attributes on a directory

s3: smbd. Generic fix for incorrect reporting of stream dos attributes on a directory

According to MS-FSA a stream name does not have
separate DOS attribute metadata, so we must return
the DOS attribute from the base filename. With one caveat,
a non-default stream name can never be a directory.

As this is common to all streams data stores, we handle
it here instead of inside all stream VFS modules.

Otherwise identical logic would have to be added to
all streams modules in their [f]get_dos_attribute_fn()
VFS calls.

Found in real-world use case by Andrew Walker <awalker@ixsystems.com>.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13380

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Böhme <slow@samba.org>