RFR: 8372552: unhandled oop in the JvmtiEventController::set_user_enabled

[Leonid Mesnik]

The issue reproduced by running test 
vmTestbase/nsk/jvmti/AttachOnDemand/attach022[1]/TestDescription.java
with `-XX:+CheckUnhandledOops`.

No need to flush object free events during VM init. So it is fine to move it after handling the oop.

Testing with tier1-5.

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Commit messages:
 - fixed handling

Changes: https://git.openjdk.org/jdk/pull/28500/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28500&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372552
  Stats: 10 lines in 1 file changed: 5 ins; 4 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28500.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28500/head:pull/28500

PR: https://git.openjdk.org/jdk/pull/28500