ap_sub_req_lookup_dirent: fix mod_negotiation loop with near infinite

subrequests

this function has been creating bogus subrequest URIs when there is
path_info for a long time.  They didn't matter until fixup_dir started
using them for URI subrequests, which led to a loop with ever growing
bogus internal URIs and filenames.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@93035 13f79535-47bb-0310-9956-ffa450edef68