s3-vfs: Fix stream_depot vfs module on btrfs.
Checking if the directory is empty using 'nlink == 2' only checks if
there are no subdirectories. It doesn't indicate if there are files in
the directory. However checking link count for no subdirectories is
wrong and applications shouldn't rely on it, see:
https://lkml.org/lkml/2012/2/1/756
Bug: https://bugzilla.samba.org/show_bug.cgi?id=10467
Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: David Disseldorp <ddiss@samba.org>
(cherry picked from commit
654b784e9c9c3563afd1af853f4795117c258e56)