RFR: 8361602: [TESTBUG] serviceability/HeapDump/UnmountedVThreadNativeMethodAtTop.java deadlocks on exception

[Richard Reingruber]

This pr moves the `notify()` call to the finally block to avoid the deadlock in `join()` if `verifyHeapDump(dumpFile)` throws an exception.

Testing was done with fastdebug and release builds on the main platforms and also on Linux/PPC64le and AIX.

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Commit messages:
 - Notify in finally block to avoid deadlock reaching there by exception

Changes: https://git.openjdk.org/jdk/pull/26213/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26213&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361602
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26213.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26213/head:pull/26213

PR: https://git.openjdk.org/jdk/pull/26213