RFR: 8341997: Tests create files in src tree instead of scratch dir

[Brian Burkhalter]

Change property `test.src` to `test.dir`.

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Commit messages:
 - 8341997: Tests create files in src tree instead of scratch dir

Changes: https://git.openjdk.org/jdk/pull/21503/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21503&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341997
  Stats: 6 lines in 3 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/21503.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21503/head:pull/21503

PR: https://git.openjdk.org/jdk/pull/21503