Fix overriding ExtendedStatus to "off" with mod_systemd loaded, and

Fix overriding ExtendedStatus to "off" with mod_systemd loaded, and
give more feedback to systemd during a reload.

* modules/arch/unix/mod_systemd.c (systemd_pre_config): New
  function; tell systemd the service is reloading here.
  (systemd_pre_mpm): Don't set ap_extended_status here, do nothing
  if ExtendedStatus is off.
  (register_hooks): Register pre_config hook.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1802251 13f79535-47bb-0310-9956-ffa450edef68