Flaky-test: PulsarSinkE2ETest.shutdown(org.apache.pulsar.io.PulsarSinkE2ETest)

PulsarSinkE2ETest is flaky. The shutdown(org.apache.pulsar.io.PulsarSinkE2ETest) test method fails sporadically.

https://github.com/apache/pulsar/runs/4942620767?check_suite_focus=true

```
Error: shutdown(org.apache.pulsar.io.PulsarSinkE2ETest) Time elapsed: 10.1 s <<< FAILURE!
java.util.concurrent.CompletionException: org.apache.pulsar.metadata.api.MetadataStoreException$BadVersionException: org.apache.zookeeper.KeeperException$BadVersionException: KeeperErrorCode = BadVersion for /loadbalance/brokers/localhost:34747
at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:331)
at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:346)
at java.base/java.util.concurrent.CompletableFuture$UniRun.tryFire(CompletableFuture.java:777)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
at java.base/java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:2088)
at org.apache.pulsar.metadata.impl.ZKMetadataStore.handleDeleteResult(ZKMetadataStore.java:262)
at org.apache.pulsar.metadata.impl.ZKMetadataStore.lambda$batchOperation$6(ZKMetadataStore.java:174)
at org.apache.pulsar.metadata.impl.PulsarZooKeeperClient$3$1.processResult(PulsarZooKeeperClient.java:490)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:722)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:563)
Caused by: org.apache.pulsar.metadata.api.MetadataStoreException$BadVersionException: org.apache.zookeeper.KeeperException$BadVersionException: KeeperErrorCode = BadVersion for /loadbalance/brokers/localhost:34747
at org.apache.pulsar.metadata.impl.ZKMetadataStore.getException(ZKMetadataStore.java:420)
... 5 more
Caused by: org.apache.zookeeper.KeeperException$BadVersionException: KeeperErrorCode = BadVersion for /loadbalance/brokers/localhost:34747
at org.apache.zookeeper.KeeperException.create(KeeperException.java:122)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:54)
at org.apache.pulsar.metadata.impl.ZKMetadataStore.getException(ZKMetadataStore.java:416)
... 5 more
```

Start with the PulsarSinkE2ETest.shutdown test and reproduce it repeatedly using the linked CI run as context. Trace the reported failure through ZKMetadataStore.java and PulsarZooKeeperClient.java, then verify that repeated executions no longer fail with the BadVersionException shown in the issue.

Written by the indexing model from the issue text.