More mod_cache tweakage...

* modules/cache/mod_cache.c

  (cache_save_filter): Instead of unconditionally returning a 304 when
   the original request was conditional and we issued a cache revalidating
   request, handle the request as if it came in while our cache was
   still valid.


* modules/cache/cache_storage.c

  (cache_select_url): Strip off the conditional headers from the original
   request, prior to adding our own for the purpose of revalidating our
   cached response.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@156330 13f79535-47bb-0310-9956-ffa450edef68