fix flaky test in AdminApiOffloadTest

[hangc0276]

Motivation

Fix flaky test in AdminApiOffloadTest.
When namespace level offload policy and topic level offload policy both not set, the offloadPolicies filed will be null.

managedLedgerConfig.setLedgerOffloader(pulsar.getManagedLedgerOffloader(namespace, offloadPolicies));

public LedgerOffloader getManagedLedgerOffloader(NamespaceName namespaceName, OffloadPoliciesImpl offloadPolicies) {
        if (offloadPolicies == null) {
            return getDefaultOffloader();
        }
        return ledgerOffloaderMap.compute(namespaceName, (ns, offloader) -> {
            try {
                if (offloader != null && Objects.equals(offloader.getOffloadPolicies(), offloadPolicies)) {
                    return offloader;
                } else {
                    if (offloader != null) {
                        offloader.close();
                    }
                    return createManagedLedgerOffloader(offloadPolicies);
                }
            } catch (PulsarServerException e) {
                LOG.error("create ledgerOffloader failed for namespace {}", namespaceName.toString(), e);
                return new NullLedgerOffloader();
            }
        });
    }

Then in getManagedLedgerOffloader method, it will return getDefaultOffloader. And the test will get the following exception.

[ERROR] testTopicLevelOffloadNonPartitioned(org.apache.pulsar.broker.admin.AdminApiOffloadTest)  Time elapsed: 0.569 s  <<< FAILURE!
java.lang.AssertionError: expected [s3] but found [NullLedgerOffloader]
	at org.testng.Assert.fail(Assert.java:99)
	at org.testng.Assert.failNotEquals(Assert.java:1037)
	at org.testng.Assert.assertEqualsImpl(Assert.java:140)
	at org.testng.Assert.assertEquals(Assert.java:122)
	at org.testng.Assert.assertEquals(Assert.java:629)
	at org.testng.Assert.assertEquals(Assert.java:639)
	at org.apache.pulsar.broker.admin.AdminApiOffloadTest.testOffload(AdminApiOffloadTest.java:360)
	at org.apache.pulsar.broker.admin.AdminApiOffloadTest.testTopicLevelOffloadNonPartitioned(AdminApiOffloadTest.java:267)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:132)
	at org.testng.internal.InvokeMethodRunnable.runOne(InvokeMethodRunnable.java:45)
	at org.testng.internal.InvokeMethodRunnable.call(InvokeMethodRunnable.java:73)
	at org.testng.internal.InvokeMethodRunnable.call(InvokeMethodRunnable.java:11)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Modification

1. Add doReturn inspection for offloadPolicies is null.

[315157973]

Why doesn't it appear every time?

[hangc0276]

Why doesn't it appear every time?

@315157973 because in current topic offload policy implementation, it doesn't refresh managedLedger configuration when topic offload policy updated, such as remote topic offload policy. When i fix the topic policy listener in #11021 , the test failed.