RFR: 8284233: serviceability/jvmti/vthread/InterruptThreadTest/InterruptThreadTest.java failing in loom repo

[Serguei Spitsyn]

The test has a lack of synchronization.
The fix is to wait for target virtual thread reaching the desired state of execution.
The fix is being tested with 100 of mach5 test runs on all platforms.

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Commit messages:
 - fix trailing space
 - 8284233: serviceability/jvmti/vthread/InterruptThreadTest/InterruptThreadTest.java failing in loom repo

Changes: https://git.openjdk.java.net/loom/pull/169/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=169&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284233
  Stats: 11 lines in 1 file changed: 9 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/loom/pull/169.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/169/head:pull/169

PR: https://git.openjdk.java.net/loom/pull/169