Stabilize TestUpdateWorkflow

[alirezazamani]

Issues

• My PR addresses the following Helix issues and references them in the PR title:
  Fixes TestUpdateWorkflow is unstable #1134

Description

• Here are some details about my PR, including screenshots of any UI changes:
  In this PR, Thread.sleep usages have been removed from TestUpdateWorkflow and replaced with TestHelper.verify.

Tests

• The following is the result of the "mvn test" command on the appropriate module:

helix-core:

[INFO] Tests run: 1151, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 4,808.221 s - in TestSuite
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 1151, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  01:20 h
[INFO] Finished at: 2020-07-01T19:57:47-07:00
[INFO] ------------------------------------------------------------------------

helix-rest:

[INFO] Tests run: 163, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 41.365 s - in TestSuite
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 163, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  46.985 s
[INFO] Finished at: 2020-07-01T20:13:47-07:00
[INFO] ------------------------------------------------------------------------

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines, and I have squashed multiple commits if they address the same issue. 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