Fix problem with the previous patch to handle HEAD requests. Now, the

header_filter will stay installed in the filter chain when processing
HEAD requests to intercept and discard content bodys sent by poorly
written handlers. This work also points out the need for an optimization
in the content_length filter to not split the brigade if the next bucket
in the brigade is an EOS.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89679 13f79535-47bb-0310-9956-ffa450edef68