backport http://svn.apache.org/r1695583 from trunk:

mod_dir: when we bail out of fixups, make sure Content-Type is not still
httpd/unix-directory.  This only happens when the generator sets
no content-type which is more common w/ no DefaultType in 2.4.

Submitted By: covener
Reviewed By: ylavic, niq



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1698384 13f79535-47bb-0310-9956-ffa450edef68