mod_cache: avoid unlikely access to freed memory.

git-svn-id: http://svn.apache.org/repos/asf/httpd/httpd/trunk@1632740 13f79535-47bb-0310-9956-ffa450edef68
mod_buffer: avoid unlikely access to freed memory and forward flushed buckets
            immediatly.


git-svn-id: http://svn.apache.org/repos/asf/httpd/httpd/trunk@1632742 13f79535-47bb-0310-9956-ffa450edef68