Relax checks for OCSP responder URIs:

* modules/ssl/ssl_engine_ocsp.c (determine_responder_uri): Allow
  NULL path; use default port for given schem.

* modules/ssl/ssl_util_ocsp.c (serialize_request): Use / if no path
  specified.

Submitted by: Kaspar Brand <asfbugz velox.ch>
PR: 45522


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@683242 13f79535-47bb-0310-9956-ffa450edef68