public void close() {
        sessionOpen = false;
        try{
            context.log(log, Level.FINE, () -> "Trying to close ZooKeeper session 0x"
                    + Long.toHexString(session.getSessionId()));
            session.close();
        } catch (InterruptedException e) {
            context.log(log, Level.WARNING, "Got interrupt exception while closing session: " + e);
        }
    }
If this is called, we assume we're in shutdown situation, or we are doing it because we need a new session.
Thus we only need to free up resources, no need to notify anyone.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/ZooKeeperDatabase.java