Guard against allowing intermediate caching when cookies are present

Guard against allowing intermediate caching when cookies are present

Output cache-control headers that disable intermediate caching even if
OutputPage->mEnableClientCache is true when the response includes
set-cookie headers as well. This change mirrors logic that has been in
use on the Wikimedia Foundation production cluster's Varnish cache
system for over 2 years to guard against accidentally caching backend
responses which include Set-Cookie headers.

Co-Author: Max Semenik <maxsem.wiki@gmail.com>
Bug: T127993
Change-Id: I1a0d38a5b9dba754b91a7832371b3dc0df51bd5a