restore http://svn.apache.org/viewvc?view=revision&revision=233369 
under a configurable option: don't run mod_dir if r->handler is already set.

PR53794



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1557640 13f79535-47bb-0310-9956-ffa450edef68