Merge r327590 from trunk:

* Fix PR37145 (data loss with httpd-2.0.55 reverse proxy method=post) by
  exchanging APR_BRIGADE_CONCAT with ap_save_brigade to ensure that
  transient buckets get setaside correctly between various iterations of
  ap_get_brigade calls.

Submitted by: rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@372046 13f79535-47bb-0310-9956-ffa450edef68