set bookieMappingCache into conf (apache#8844)

### Motivation
When the value of "/bookies" in ZooKeeper is changed, Brokers are notified of the change.
After the notification to Brokers, only one of the two BookKeeper clients that Brokers have seems to reflect the change.

**Two BookKeeper clients that Brokers have**
- https://github.com/apache/pulsar/blob/ac0c6e41f0ebe3c900bb31e41c8d40b3f60b19df/pulsar-broker/src/main/java/org/apache/pulsar/broker/ManagedLedgerClientFactory.java#L81
- https://github.com/apache/pulsar/blob/102fa9de03509b86e47f58ab8e1c0dde2095da3b/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/schema/BookkeeperSchemaStorage.java#L105

The client of `BookkeeperSchemaStorage` don't seems to reflect the change.
The cause is that `ZkBookieRackAffinityMapping#onUpdate` don't run.

I confirmed that I change ZkBookieRackAffinityMapping instances to use same `ZooKeeperDataCache` and `ZkBookieRackAffinityMapping#onUpdate` works.

### Modification
- Set the argument of `ZkBookieRackAffinityMapping#setConf` to `bookieMappingCache`
- Move `updateRacksWithHost()`

pulsar-zookeeper-utils/src/main/java/org/apache/pulsar/zookeeper/ZkBookieRackAffinityMapping.java

@@ -54,6 +54,7 @@ public class ZkBookieRackAffinityMapping extends AbstractDNSToSwitchMapping
     private static final Logger LOG = LoggerFactory.getLogger(ZkBookieRackAffinityMapping.class);
 
     public static final String BOOKIE_INFO_ROOT_PATH = "/bookies";
+    public static final String ZK_DATA_CACHE_BK_RACK_CONF_INSTANCE = "zk_data_cache_bk_rack_conf_instance";
 
     private ZooKeeperDataCache<BookiesRackConfiguration> bookieMappingCache = null;
     private ITopologyAwareEnsemblePlacementPolicy<BookieNode> rackawarePolicy = null;
@@ -66,7 +67,13 @@ public class ZkBookieRackAffinityMapping extends AbstractDNSToSwitchMapping
     @Override
     public void setConf(Configuration conf) {
         super.setConf(conf);
-        bookieMappingCache = getAndSetZkCache(conf);
+        if (conf.getProperty(ZK_DATA_CACHE_BK_RACK_CONF_INSTANCE) != null) {
+            bookieMappingCache = (ZooKeeperDataCache<BookiesRackConfiguration>) conf.getProperty(ZK_DATA_CACHE_BK_RACK_CONF_INSTANCE);
+            bookieMappingCache.registerListener(this);
+        } else {
+            bookieMappingCache = getAndSetZkCache(conf);
+            conf.setProperty(ZK_DATA_CACHE_BK_RACK_CONF_INSTANCE, bookieMappingCache);
+        }
 
         try {
             BookiesRackConfiguration racks = bookieMappingCache.get(BOOKIE_INFO_ROOT_PATH).orElse(new BookiesRackConfiguration());
@@ -152,7 +159,6 @@ public BookiesRackConfiguration deserialize(String key, byte[] content)
                     LOG.debug("Loading the bookie mappings with bookie info data: {}", new String(content));
                 }
                 BookiesRackConfiguration racks = jsonMapper.readValue(content, BookiesRackConfiguration.class);
-                updateRacksWithHost(racks);
                 return racks;
             }
 
@@ -172,6 +178,7 @@ private String getRack(String bookieAddress) {
         try {
             // Trigger load of z-node in case it didn't exist
             Optional<BookiesRackConfiguration> racks = bookieMappingCache.get(BOOKIE_INFO_ROOT_PATH);
+            updateRacksWithHost(racks.orElse(new BookiesRackConfiguration()));
             if (!racks.isPresent()) {
                 // since different placement policy will have different default rack,
                 // don't be smart here and just return null

pulsar-zookeeper-utils/src/test/java/org/apache/pulsar/zookeeper/ZkBookieRackAffinityMappingTest.java

@@ -19,6 +19,8 @@
 package org.apache.pulsar.zookeeper;
 
 import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNotNull;
+import static org.testng.Assert.assertNull;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.collect.Lists;
@@ -78,12 +80,14 @@ public void testBasic() throws Exception {
         ClientConfiguration bkClientConf1 = new ClientConfiguration();
         bkClientConf1.setProperty(ZooKeeperCache.ZK_CACHE_INSTANCE, new ZooKeeperCache("test", localZkc, 30) {
         });
+        assertNull(bkClientConf1.getProperty(ZkBookieRackAffinityMapping.ZK_DATA_CACHE_BK_RACK_CONF_INSTANCE));
         mapping1.setConf(bkClientConf1);
         List<String> racks1 = mapping1
                 .resolve(Lists.newArrayList(BOOKIE1.getHostName(), BOOKIE2.getHostName(), BOOKIE3.getHostName()));
         assertEquals(racks1.get(0), "/rack0");
         assertEquals(racks1.get(1), "/rack1");
         assertEquals(racks1.get(2), null);
+        assertNotNull(bkClientConf1.getProperty(ZkBookieRackAffinityMapping.ZK_DATA_CACHE_BK_RACK_CONF_INSTANCE));
 
         // Case 2: ZkServers and ZkTimeout are given (ZKCache will be constructed in
         // ZkBookieRackAffinityMapping#setConf)