[jdk11u-dev] RFR: 8273831: PrintServiceLookup spawns 2 threads in the current classloader, getting orphaned

[Ben Taylor]

Clean backport of JDK-8273831 to fix a regression that can leave an orphaned thread. Verified with included test.

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Commit messages:
 - Backport 687567822a5380fb7d8c5b54ae548b2a5c848187

Changes: https://git.openjdk.org/jdk11u-dev/pull/2623/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2623&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8273831
  Stats: 120 lines in 3 files changed: 104 ins; 3 del; 13 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2623.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2623/head:pull/2623

PR: https://git.openjdk.org/jdk11u-dev/pull/2623