* In the case that we fail to read the response line from the backend and if

  we are a reverse proxy request shutdown the connection WITHOUT ANY response
  to trigger a retry by the client if allowed (as for idempotent requests).
  BUT currently we should not do this if the request is the first request on
  a keepalive connection as browsers like seamonkey only display an empty page
  in this case and do not do a retry.

Related to PR 37770



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@645813 13f79535-47bb-0310-9956-ffa450edef68