public void unlock() {
            if (lock != null) try {
                logger.log(INFO, "Relinquishing lease for " + id);
                lock.close();
            }
            catch (Exception e) {
                logger.log(WARNING, "Failed closing " + lock, e);
            }
            doom.set(EMPTY);
            lock = null;
        }
Invalidate all leases, due to connection loss.
zkfacade/src/main/java/com/yahoo/vespa/curator/SingletonManager.java