*) mod_session_cookie: avoid duplicate Set-Cookie headers in the response.

   trunk patch: http://svn.apache.org/r1843244
+1: elukey, jim, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1847288 13f79535-47bb-0310-9956-ffa450edef68