Fix TestHelixViewAggregator test

[qqu0127]

Issues

• [X] My PR addresses the following Helix issues and references them in the PR description: Fixes https://github.com/apache/helix/issues/2049

Description

• [X] Here are some details about my PR, including screenshots of any UI changes: CI test history shows that test TestHelixViewAggregator is unstable. We suspect two causes:

1. Delayed rebalance triggered during testing.
2. Cluster events from previous test received after monitor reset therefore overlap with the following tests.

This PR disables delayed rebalance for the source clusters in the test, and updates the event verification logic.

Tests

• [X] The following tests are written for this issue:

Local test passed.

• The following is the result of the "mvn test" command on the appropriate module: [INFO] Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 60.877 s - in TestSuite [INFO] [INFO] Results: [INFO] [INFO] Tests run: 13, Failures: 0, Errors: 0, Skipped: 0 [INFO] [INFO] [INFO] --- jacoco-maven-plugin:0.8.6:report (generate-code-coverage-report) @ helix-view-aggregator --- [INFO] Loading execution data file /home/qqu/workspace/qqu-helix/helix-view-aggregator/target/jacoco.exec [INFO] Analyzed bundle 'Apache Helix :: View Aggregator' with 15 classes [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 01:07 min [INFO] Finished at: 2022-06-30T14:02:03-07:00 [INFO] ------------------------------------------------------------------------

Changes that Break Backward Compatibility (Optional)

• My PR contains changes that break backward compatibility or previous assumptions for certain methods or API. They include:

(Consider including all behavior changes for public methods or API. Also include these changes in merge description so that other developers are aware of these changes. This allows them to make relevant code changes in feature branches accounting for the new method/API behavior.)

Documentation (Optional)

• In case of new functionality, my PR adds documentation in the following wiki page:

(Link the GitHub wiki you added)

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

• My diff has been formatted using helix-style.xml (helix-style-intellij.xml if IntelliJ IDE is used)