[jdk11u-dev] RFR: 8264512: jdk/test/jdk/java/util/prefs/ExportNode.java relies on default platform encoding

[Goetz Lindenmaier]

I backport this for parity with 11.0.19-oracle.

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Commit messages:
 - Backport 104e925dfdac0af3b1c6862f9a7d3442484f9241

Changes: https://git.openjdk.org/jdk11u-dev/pull/1755/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1755&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8264512
  Stats: 39 lines in 1 file changed: 21 ins; 0 del; 18 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1755.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1755/head:pull/1755

PR: https://git.openjdk.org/jdk11u-dev/pull/1755