change error handling for bad resp headers

 - avoid looping between ap_die and the http filter
 - remove the header that failed the check
 - keep calling apr_table_do until our fn stops matching


This is still not great. We get the original body, a 500 status
code and status line.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1773285 13f79535-47bb-0310-9956-ffa450edef68