Fix a problem in proxy where headers from other modules were

added to the response headers when this was already done in the
core already. This resulted in header (and therefore cookie)
duplication.
PR:
Obtained from:
Submitted by:	Martijn Schoemaker <martijn@osp.nl>
Reviewed by:	Graham Leggett


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@96620 13f79535-47bb-0310-9956-ffa450edef68