Backport fix r230718; a soon-to-be impossible edge case; we are always
  sending a body (even an 'empty' body) using stream_chunked, so we must
  always send the trailing "0" end of body marker.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/proxy-reqbody-2.0.x@230719 13f79535-47bb-0310-9956-ffa450edef68