smbd: Make SMB3 clients use encryption with "smb encrypt = auto"

smbd: Make SMB3 clients use encryption with "smb encrypt = auto"

Slight modification for 4.1 by Michael Adam <obnox@samba.org>
(s/xconn/conn/ in smb2_sesssetup.c)

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11372

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Tue Mar  3 10:40:42 CET 2015 on sn-devel-104

(cherry picked from commit b3385f74db54bd8a07a0be5515151b633c067da4)