[jdk21u-dev] RFR: 8320830: [AIX] Dont mix os::dll_load() with direct dlclose() calls

[Martin Doerr]

Backport of [JDK-8320830](https://bugs.openjdk.org/browse/JDK-8320830).

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Commit messages:
 - Backport 61653a1ff166816a6af6875c42bcd85023f3859d

Changes: https://git.openjdk.org/jdk21u-dev/pull/86/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=86&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320830
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/86.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/86/head:pull/86

PR: https://git.openjdk.org/jdk21u-dev/pull/86