* run the request_status hook in proxy_handler if HTTP_SERVICE_UNAVAILABLE

  is returned by ap_proxy_pre_request.

Suggested by: Brian Akins <brian.akins turner.com>, Mladen Turk
Reviewed by: Jim Jagielski


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@293123 13f79535-47bb-0310-9956-ffa450edef68