set expiry time correctly.

set Cookie on err_headers_out, and ensure it is only set once.

PR: 12132
Submitted by:	apachecvslog@robcromwell.com (Rob Cromwell)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96577 13f79535-47bb-0310-9956-ffa450edef68