Merge r693392 from trunk:

* If CPING fails retry once more with a fresh TCP connection. If this fails
  as well give up.

Submitted by: rpluem
Reviewed by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@696322 13f79535-47bb-0310-9956-ffa450edef68