Optional<ThreadLockStats> getThreadLockStatsHolding(String lockPath) {
        return Optional.ofNullable(lockPathsHeld.get(lockPath)).map(statsByThread::get);
    }
Returns the ThreadLockStats holding the lock on the path, but the info may be outdated already
on return, either no-one holds the lock or another thread may hold the lock.
zkfacade/src/main/java/com/yahoo/vespa/curator/stats/LockStats.java