Cothread: Ensure cosocket test works in presence of http_proxy environment

git-svn-id: svn+ssh://serv0002.cs.diamond.ac.uk/home/subversion/repos/controls/diamond/trunk/python/cothread@112107 e099a375-04f9-0310-9d5f-a741eaff62e1
Merge branch 'master' into python3