If we have the response for a non-Range request in the memory cache, we
would previously use it in reply to Range requests. Similar to commit
878b00ae61f998a26aad7f50fae66cf969878ad6, we are just punting on Range
requests in the HTTP caches for now.
Our HTTP disk cache is currently manually tested against various sites.
This patch adds some tests to cover various scenarios, including non-
cacheable responses, expired responses, and revalidation.
In order to ensure we hit the disk cache in RequestServer, we must
disable the in-memory cache in WebContent.