Perform OCSP requests via HTTP/1.1 instead of HTTP/1.0

Perform OCSP requests via HTTP/1.1 instead of HTTP/1.0

According to https://docs.digicert.com/en/whats-new/change-log/certcentral-change-log.html#digicert-ending-support-for-http-1-0-connections-for-ocsp-and-crl-certificate-status-verification-checks-619426
Digicert stops supporting HTTP/1.0 for their OCSP responder, but still supports
HTTP/1.1. Hence switch to HTTP/1.1 to keep things working.
It is assumed that other OCSP responders support HTTP/1.1 as well.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1928222 13f79535-47bb-0310-9956-ffa450edef68