ISSUE-17388: Flaky-test: PersistentSubscriptionMessageDispatchStreamingDispatcherThrottlingTest.testMultiLevelDispatch

[sijie]

Original Issue: apache#17388

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PersistentSubscriptionMessageDispatchStreamingDispatcherThrottlingTest.testMultiLevelDispatch is flaky. It fails sporadically.

Example failure

Example failure

Exception stacktrace

Error:  Failures: 
[2359](https://github.com/apache/pulsar/runs/8115929202?check_suite_focus=true#step:10:2361)
  Error:  org.apache.pulsar.broker.service.persistent.PersistentSubscriptionMessageDispatchStreamingDispatcherThrottlingTest.testMultiLevelDispatch(org.apache.pulsar.broker.service.persistent.PersistentSubscriptionMessageDispatchStreamingDispatcherThrottlingTest)
[2360](https://github.com/apache/pulsar/runs/8115929202?check_suite_focus=true#step:10:2362)
  [INFO]   Run 1: PASS
[2361](https://github.com/apache/pulsar/runs/8115929202?check_suite_focus=true#step:10:2363)
  Error:    Run 2: PersistentSubscriptionMessageDispatchStreamingDispatcherThrottlingTest>SubscriptionMessageDispatchThrottlingTest.testMultiLevelDispatch:503->SubscriptionMessageDispatchThrottlingTest.testDispatchRate:478 expected [true] but found [false]
[2362](https://github.com/apache/pulsar/runs/8115929202?check_suite_focus=true#step:10:2364)
  [INFO]   Run 3: PASS

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