List<LockAttempt> asList() {
        synchronized (monitor) {
            return List.copyOf(byLockPath.values());
        }
    }
Priority queue containing all samples.  The head of this queue (peek()/poll())
returns the LockAttempt with the smallest duration.
zkfacade/src/main/java/com/yahoo/vespa/curator/stats/LockAttemptSamples.java