[jdk11u] RFR: 8315683: Parallelize java/util/concurrent/tck/JSR166TestCase.java

[Soumadipta Roy]

Backport 4415261688dc258b6d254668bcf8818c61cc65ea to JDK11u.

Backporting the fix for https://bugs.openjdk.org/browse/JDK-8315683 merged as part of https://github.com/openjdk/jdk/pull/15619. https://github.com/openjdk/jdk/commit/4415261688dc258b6d254668bcf8818c61cc65ea.patch could not be cleanly applied as `@run junit/othervm/timeout=1000 -Djava.security.manager=allow JSR166TestCase` is not applicable for JDK11.

The tests passed in release mode in linux_x86_64 with time: **462.54s user 21.92s system 1099% cpu 44.077 total**
Before it was: **325.80s user 21.64s system 534% cpu 1:05.04 total**

Passed: java/util/concurrent/tck/JSR166TestCase.java#default
Passed: java/util/concurrent/tck/JSR166TestCase.java#others
Passed:
java/util/concurrent/tck/JSR166TestCase.java#forkjoinpool-common-parallelism
Test results: passed: 3

-------------

Commit messages:
 - 8315683: Parallelize java/util/concurrent/tck/JSR166TestCase.java

Changes: https://git.openjdk.org/jdk11u/pull/84/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u&pr=84&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315683
  Stats: 26 lines in 1 file changed: 19 ins; 4 del; 3 mod
  Patch: https://git.openjdk.org/jdk11u/pull/84.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u.git pull/84/head:pull/84

PR: https://git.openjdk.org/jdk11u/pull/84