mod_cache: r->err_headers_out is not merged into

r->headers when mod_cache is enabled and the response
is cached for the first time.

Submitted by: elu
Reviewed by: ylavic, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1705528 13f79535-47bb-0310-9956-ffa450edef68