Remove the hack from r806010 that mis-uses the pointer to the per-directory

Remove the hack from r806010 that mis-uses the pointer to the per-directory
config for other things. This breaks with MPMs that do have a per-directory
config.

If any module appears that wants to use this functionality, we can
add a new, non-broken API. Since the docs clearly state that ap_set_listener()
should not be called by external modules, I don't consider this an API/ABI
change, but only a bug fix.

PR: 52904

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1304874 13f79535-47bb-0310-9956-ffa450edef68