ldb: cmocka test for empty attributes bug

ldb: cmocka test for empty attributes bug

Cmocka test exposing LDB bug where a request with an empty attributes
list returns a response containing all attributes.  The bug is in the
ACL module and will be fixed in the next commit.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13836

Signed-off-by: Aaron Haslett <aaronhaslett@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
(cherry picked from commit 24efa3ca5399d5cf538c3be504014a954685f1ed)