Merge r1597352 from trunk:

* Give ap_proxy_post_request as chance to act correctly on the status code
  by setting r->status temporarily to access_status. r->status might be
  different than access_status e.g. r->status could be HTTP_OK if e.g. we
  override the error page on the proxy or if the error was not generated
  by the backend itself but by the proxy e.g. a bad gateway.

Submitted by: rpluem
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1701411 13f79535-47bb-0310-9956-ffa450edef68