* If the mod_proxy backend connection broke in the middle of the response,

  then
  - Do not cache it.
  - Signal the client that something went wrong by closing the connection
    and not sending the last-chunk marker if the response was T-E chunked.

server/core_filters.c         : Close the connection to the client by setting
                                c->keepalive to AP_CONN_CLOSE.
modules/http/chunk_filter.c   : Do not send last-chunk marker in the case
                                the backend broke.
modules/proxy/mod_proxy_http.c: Signal that the backend connection broke.
modules/cache/mod_disk_cache.c: Respect r->no_cache for discarding the response


Submitted by: Roy T. Fielding, Jim Jagielski, Ruediger Pluem
Reviewed by: Roy T. Fielding, Jim Jagielski, Ruediger Pluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@357461 13f79535-47bb-0310-9956-ffa450edef68