[improve][broker]Reduce the frequency of calls to the LockManager#listLocks method.

[lordcheng10]

Motivation

In the cleanupDeadBrokersData method, the ModularLoadManagerImpl#getAvailableBrokers method will be called every time, in which LockManager#listLocks will be called:

pulsar/pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/impl/ModularLoadManagerImpl.java

Lines 482 to 494 in 08df28a

	private void cleanupDeadBrokersData() {
	final Set<String> activeBrokers = getAvailableBrokers();
	final Set<String> knownBrokersCopy = new HashSet<>(this.knownBrokers);
	Collection<String> newBrokers = CollectionUtils.subtract(activeBrokers, knownBrokersCopy);
	this.knownBrokers.addAll(newBrokers);
	Collection<String> deadBrokers = CollectionUtils.subtract(knownBrokersCopy, activeBrokers);
	this.knownBrokers.removeAll(deadBrokers);
	if (pulsar.getLeaderElectionService() != null
	&& pulsar.getLeaderElectionService().isLeader()) {
	deadBrokers.forEach(this::deleteTimeAverageDataFromMetadataStoreAsync);
	}
	}

For non-leader nodes, it can return directly without executing the listLocks method.

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