void fenceZombieSourceTasks(final String connName, final Callback<Void> callback) {
        addRequest(() -> {
            doFenceZombieSourceTasks(connName, callback);
            return null;
        }, forwardErrorAndTickThreadStages(callback));
    }
Close resources managed by this herder but which are not explicitly started.
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedHerder.java