Merge r955966 from trunk:

* Ensure that we only return a non fatal error if the request is idempotent
  and if we did not sent any request body so far.

Submitted by: rpluem
Reviewed by: rpluem, trawick, niq


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@963195 13f79535-47bb-0310-9956-ffa450edef68