follow-up to r1562472, 1561262, and 1561923:

Improve messaging...

* easier to tell what went wrong in some cases
* reduce number of debug messages without losing information in some cases


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1574151 13f79535-47bb-0310-9956-ffa450edef68