s3:smb2_sesssetup: allow a compound request after a SessionSetup

s3:smb2_sesssetup: allow a compound request after a SessionSetup

This is not a full fix yet as we don't allow compound requests
after going async.

With SMB 3.11 requiring signed TreeConnect requests it's pointless
to try to compound requests after a SessionSetup.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12845

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Jun 17 10:55:25 CEST 2017 on sn-devel-144