[jdk21u-dev] RFR: 8331063: Some HttpClient tests don't report leaks

[Amos Shi]

Backport of [JDK-8331063](https://bugs.openjdk.org/browse/JDK-8331063)

Testing
- Local: Test passed on `MacOS 14.5`
  - `ForbiddenHeadTest.java`: Test results: passed: 1
  - `ProxySelectorTest.java`: Test results: passed: 1
- Pipeline: 
- Testing Machine:

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

Commit messages:
 - Backport e4ed7ced75c53cf5ff40c5dae4830b1ee2589802

Changes: https://git.openjdk.org/jdk21u-dev/pull/758/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=758&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331063
  Stats: 30 lines in 2 files changed: 7 ins; 0 del; 23 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/758.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/758/head:pull/758

PR: https://git.openjdk.org/jdk21u-dev/pull/758