RFR: 8321069: JvmtiThreadState::state_for_while_locked() returns nullptr for an attached JNI thread with a java.lang.Thread object after JDK-8319935

[Daniel D. Daugherty]

In the fix for the following bug:

[JDK-8319935](https://bugs.openjdk.org/browse/JDK-8319935) Ensure only one JvmtiThreadState is created for one JavaThread associated with attached native thread

JvmtiThreadState::state_for_while_locked() was changed to
return nullptr for attaching JNI threads regardless of whether
that JNI thread/JavaThread had a java.lang.Thread object.

We should only filter out a JavaThread that's attaching via JNI
if it has no java.lang.Thread object.

This fix has been tested with Mach5 Tier[1-7] and there are no related test failures.
Mach5 Tier8 is in process.

I'm going to need @jianglizhou to rerun her testing for:

[JDK-8319935](https://bugs.openjdk.org/browse/JDK-8319935) Ensure only one JvmtiThreadState is created for one JavaThread associated with attached native thread

since the test(s) for that fix are not yet integrated in the jdk/jdk repo.

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Commit messages:
 - 8321069: Test failure after JDK-8319935: exiting thread called setup_jvmti_thread_state

Changes: https://git.openjdk.org/jdk/pull/16934/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16934&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321069
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16934.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16934/head:pull/16934

PR: https://git.openjdk.org/jdk/pull/16934