[SRU trusty] [CVE-2014-0069 followup] CIFS hardening patch

[Andy Whitcroft]

When CVE-2014-0069 was fixed a second hardening patch was applied.
This fix was not part of the actual mitigation for that specific CVE
but provides further protection against similar issues in the future.
We therefore proposed applying this to the same releases to which the
CVE was applied.  Given where we are with the various release cycles
this seems most applicable to 14.04 (Utopic already has this applied).
By luck this fix was the very next fix to the CIFS file in question and
so is a clean cherry pick there.

Proposing for SRU to trusty/master.

-apw