[jdk17u-dev] RFR: 8292848: AWT_Mixing and TrayIcon tests fail on el8 with hard-coded isOel7

[Goetz Lindenmaier]

I backport this for parity with 17.0.16-oracle.

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Commit messages:
 - Backport c13e0ef3f8046a979638d6885a732553fc2b126e

Changes: https://git.openjdk.org/jdk17u-dev/pull/3279/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3279&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292848
  Stats: 69 lines in 12 files changed: 19 ins; 0 del; 50 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3279.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3279/head:pull/3279

PR: https://git.openjdk.org/jdk17u-dev/pull/3279