RFR: Use headers and other info from the most recent response

[Robin Westberg]

When a 304 response is received from a GET request, we retrieve the original request from the cache and return it instead. However, we should only reuse the cached body as other headers (such as links to further result pages) may have been updated.

-------------

Commit messages:
 - Use headers and other info from the most recent response, even if the body itself is retrieved from the cache.

Changes: https://git.openjdk.java.net/skara/pull/971/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=971&range=00
  Stats: 92 lines in 2 files changed: 89 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/971.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/971/head:pull/971

PR: https://git.openjdk.java.net/skara/pull/971