[lworld] RFR: 8336795: [lworld] JNI MonitorEnter doesn't return the right value when it throws an exception

[Frederic Parain]

Fix the value returned by JNI MonitorEnter when called on a value class instance.

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Commit messages:
 - Fix value return by JNI MonitorEnter

Changes: https://git.openjdk.org/valhalla/pull/1422/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1422&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336795
  Stats: 9 lines in 3 files changed: 7 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/valhalla/pull/1422.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1422/head:pull/1422

PR: https://git.openjdk.org/valhalla/pull/1422