BUG Fix old patch for IE no-cache https downloads.

Currently the HTTP::add_cache_headers competely overrides Cache-Control
headers on each request, so there is no way to inject custom headers
here from the API-consuning methods.

Also of note: adding no-store header also fixes the issue but will
prevent proxies from caching the request body (which they do when using
no-cache). So the setting max-age to some low number is a better choice
here.