public void shutDownNoPoison() {
        this.shutDownNoPoison = true;
    }
Set to true to shut down the FileResourceCrawler without
adding poison.  Do this only if you've already called another mechanism
to request that consumers shut down.  This prevents a potential deadlock issue
where the crawler is trying to add to the queue, but it is full.
tika-batch/src/main/java/org/apache/tika/batch/FileResourceCrawler.java