[jdk18u] RFR: 8276819: javax/print/PrintServiceLookup/FlushCustomClassLoader.java fails to free

[Sergey Bylokhov]

Hi all,
This is a test stabilization fix, additional information [here](https://github.com/openjdk/jdk/pull/6778).
This pull request contains a backport of commit [7c2c5858](https://github.com/openjdk/jdk/commit/7c2c58587d4eda5523331eae45e7d897252dc097) from the [openjdk/jdk](https://git.openjdk.java.net/jdk) repository.
The commit being backported was authored by Sergey Bylokhov on 12 Dec 2021 and was reviewed by Prasanta Sadhukhan and Alexey Ivanov.
Thanks!

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Commit messages:
 - Backport 7c2c58587d4eda5523331eae45e7d897252dc097

Changes: https://git.openjdk.java.net/jdk18u/pull/24/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=24&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276819
  Stats: 9 lines in 1 file changed: 3 ins; 4 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/24.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/24/head:pull/24

PR: https://git.openjdk.java.net/jdk18u/pull/24