RFR: 8291456: com/sun/jdi/ClassUnloadEventTest.java failed with: Wrong number of class unload events: expected 10 got 4

[Serguei Spitsyn]

The JDI ClassUnloadEvent events are synthesized by the JDWP agent from the JVM TI ObjectFree events.
The JVM TI ObjectFree events are flushed when the JVM TI SetEvenNotificationMode is used to disable the ObjectFree events. It is not very helpful for JDWP agent as the ObjectFree events are always enabled.
The fix is to flush all pending ObjectFree events at the VM shutdown.

Testing:

All mach5 jobs with JVMTI/JDI tests and tiers 1-6 were successfully passed on 3 debug platforms.

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Commit messages:
 - 8291456: com/sun/jdi/ClassUnloadEventTest.java failed with: Wrong number of class unload events: expected 10 got 4

Changes: https://git.openjdk.org/jdk/pull/10736/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10736&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291456
  Stats: 9 lines in 2 files changed: 2 ins; 5 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10736.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10736/head:pull/10736

PR: https://git.openjdk.org/jdk/pull/10736