change short-lived behavior of "DirectoryIndex None" based on feedback from wrowe:

Doesn't search for anything:
  DirectoryIndex disabled

Does search for literal "disabled":
  DirectoryIndex disabled foo.
  DirectoryIndex foo disabled 
  DirectoryIndex disabled disabled 

Does search:
  DirectoryIndex disabled.html



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@713462 13f79535-47bb-0310-9956-ffa450edef68