Flaky-test: BacklogQuotaManagerTest.testConsumerBacklogEvictionTimeQuota

BacklogQuotaManagerTest.testConsumerBacklogEvictionTimeQuota is flaky. It fails sporadically.

[example failure](https://github.com/apache/pulsar/runs/6192268507?check_suite_focus=true)

```
Error: testConsumerBacklogEvictionTimeQuota(org.apache.pulsar.broker.service.BacklogQuotaManagerTest) Time elapsed: 6.601 s <<< FAILURE!
java.lang.AssertionError: expected [4] but found [5]
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:797)
at org.testng.Assert.assertEquals(Assert.java:807)
at org.apache.pulsar.broker.service.BacklogQuotaManagerTest.testConsumerBacklogEvictionTimeQuota(BacklogQuotaManagerTest.java:484)
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)
```

Start by running BacklogQuotaManagerTest.testConsumerBacklogEvictionTimeQuota and inspect the assertion at BacklogQuotaManagerTest.java:484. Use the linked failure as a reference while investigating why the test sometimes observes 5 instead of the expected 4. Done means the test no longer fails sporadically.

Written by the indexing model from the issue text.