s4:smbcli:smb2: add a random GUID to the transport connection in smb2_transport_init()

s4:smbcli:smb2: add a random GUID to the transport connection in smb2_transport_init()

This GUID is used in the smb2 negprot when max protocol is bigger than 0x0202.
According to section 2.2.3 of the MS-SMB2 document, the Client GUID filed in the
SMB2 negotiate request must be filled with a (non-zero) GUID if there are other
dialects than 0x0202 in the dialects field.

http://msdn.microsoft.com/en-us/library/cc246543%28v=prot.13%29.aspx

Apart from corresponding to the docs, this change makes some of our durable-open
tests (e.g reopen2 and open-oplock) _not_ hang when running against windows 8
preview (which might be still buggy).

Pair-Programmed-With: Gregor Beck <gbeck@sernet.de>

Autobuild-User: Michael Adam <obnox@samba.org>
Autobuild-Date: Thu Feb 23 03:23:57 CET 2012 on sn-devel-104