Fix LoadManager shutdown timing issue (#358)

* Fix LoadManager shutdown timing issue

* Remove synchronization on close()

pulsar-broker/src/main/java/com/yahoo/pulsar/broker/loadbalance/impl/ModularLoadManagerImpl.java

@@ -575,8 +575,8 @@ public class ModularLoadManagerImpl implements ModularLoadManager, ZooKeeperCach
     @Override
     public void stop() throws PulsarServerException {
         availableActiveBrokers.close();
-        brokerDataCache.clear();
         brokerDataCache.close();
+        brokerDataCache.clear();
         scheduler.shutdown();
     }
 

pulsar-broker/src/main/java/com/yahoo/pulsar/broker/loadbalance/impl/SimpleLoadManagerImpl.java

@@ -1434,8 +1434,8 @@ public class SimpleLoadManagerImpl implements LoadManager, ZooKeeperCacheListene
 
     @Override
     public void stop() throws PulsarServerException {
-        loadReportCacheZk.clear();
         loadReportCacheZk.close();
+        loadReportCacheZk.clear();
         availableActiveBrokers.close();
         scheduler.shutdown();
     }