s3:smb2_sesssetup: implement SMB3 session bind (disabled)

s3:smb2_sesssetup: implement SMB3 session bind (disabled)

This is disabled for now. It will be possible to enabled it
via a config switch once the underpinnings are complete.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>
Pair-Programmed-With: Guenther Deschner <gd@samba.org>

Signed-off-by: Michael Adam <obnox@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Michael Adam <obnox@samba.org>
Autobuild-Date(master): Sat Jan 23 03:22:18 CET 2016 on sn-devel-144