Code review comment for lp:~leonardr/lazr.restful/cache-service-root

All right, I've changed lazr.restful to avoid triggering the httplib2 bug on old versions of lazr.restfulclient. (I've tested this version of lazr.restful with an old and a new lazr.restfulclient, and they both worked, though obviously the old one didn't get the benefit of the Cache-Control headers.)