For OPTIONS and HEAD, only 2xx and 3xx are considered "passing"

(until I implement the conditions expr testing)... honor
the pass/fail count and LOG_INFO when the health check enables
or disables a backend worker.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1725523 13f79535-47bb-0310-9956-ffa450edef68