@Override
    public String toString() {
        return "DirQueue{" +
               "rootDir=" + rootDir +
               ", writeId=" + writeId +
               ", readId=" + readId +
               '}';
    }
When we have finished with a dir we should be in a position where the dir has been
moved so can try to delete the parent directories. We never want to delete the dir
itself as it should have been moved and any failure to do so is an error.

@param dir The dir to close.
stroom-proxy/stroom-proxy-app/src/main/java/stroom/proxy/app/handler/DirQueue.java