Flaky-test: PackagesApiNotEnabledTest.testPackagesOperationsWithoutPackagesServiceEnabled

```
Error: Tests run: 4, Failures: 1, Errors: 0, Skipped: 3, Time elapsed: 6.187 s <<< FAILURE! - in org.apache.pulsar.broker.admin.v3.PackagesApiNotEnabledTest
Error: testPackagesOperationsWithoutPackagesServiceEnabled(org.apache.pulsar.broker.admin.v3.PackagesApiNotEnabledTest) Time elapsed: 0.013 s <<< FAILURE!
java.lang.AssertionError: expected [500] but found [503]
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:907)
at org.testng.Assert.assertEquals(Assert.java:917)
at org.apache.pulsar.broker.admin.v3.PackagesApiNotEnabledTest.testPackagesOperationsWithoutPackagesServiceEnabled(PackagesApiNotEnabledTest.java:55)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
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.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:833)
```

[example failure](https://github.com/apache/pulsar/runs/7175862912?check_suite_focus=true)

Start with org.apache.pulsar.broker.admin.v3.PackagesApiNotEnabledTest.testPackagesOperationsWithoutPackagesServiceEnabled and inspect the assertion at PackagesApiNotEnabledTest.java:55. Re-run this test using the linked failure as a reference and compare the expected 500 response with the observed 503. Done means the test consistently passes with the intended status when the packages service is disabled.

Written by the indexing model from the issue text.