RFR: 8257836: Add additional test cases to TestSyncOnValueBasedClassEvent.java

[Harold Seigel]

Please review this small change to add additional test cases to TestSyncOnValueBasedClassEvent.java.  The modified test was tested using Mach5 on Linux x64, Linux aarch64, Mac OS and Windows.

Thanks, Harold

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Commit messages:
 - 8257836: Add additional test cases to TestSyncOnValueBasedClassEvent.java

Changes: https://git.openjdk.java.net/jdk/pull/3465/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3465&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257836
  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3465.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3465/head:pull/3465

PR: https://git.openjdk.java.net/jdk/pull/3465