s3: tests: Regression test to ensure we can never return a DIRECTORY attribute on...

s3: tests: Regression test to ensure we can never return a DIRECTORY attribute on a stream.

Tests streams_xattr and also streams_depot.

Inspired from a real-world test 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>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Thu Apr 12 02:04:28 CEST 2018 on sn-devel-144

(cherry picked from commit 82beaf868f252c4bc975ddafd80240af6f679b83)