Close ZK before canceling future with exception (#6228) (#6399)

Fixes #6228

(cherry picked from commit e6a631d)

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

@@ -55,6 +55,7 @@ public CompletableFuture<ZooKeeper> create(String serverList, SessionType sessio
                         .build();
 
                 if (zk.getState() == States.CONNECTEDREADONLY && sessionType != SessionType.AllowReadOnly) {
+                    zk.close();
                     future.completeExceptionally(new IllegalStateException("Cannot use a read-only session"));
                 }