[jdk21u-dev] RFR: 8342609: jpackage test helper function incorrectly removes a directory instead of its contents only

[Goetz Lindenmaier]

I backport this for parity with 21.0.7-oracle.

Resolved Copyright, probably clean anyways.

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Commit messages:
 - Backport 7133d1b983d7b85ba3c8dde26eb654c7ab695b07

Changes: https://git.openjdk.org/jdk21u-dev/pull/1286/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1286&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342609
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1286.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1286/head:pull/1286

PR: https://git.openjdk.org/jdk21u-dev/pull/1286