@Override
    public void close() throws IOException {
        // the endpoint is closed in a finally{} block inside AbstractHttpRequestHandler
        // this class should be possible to close willynilly as it is exposed to plug-ins
        flush();
    }
Flush the internal buffers, does not touch the ContentChannel.
container-core/src/main/java/com/yahoo/container/jdisc/ContentChannelOutputStream.java