RFR: 8377457: java/util/logging/ParentLoggersTest.java failed intermittently

[Daniel Fuchs]

`java/util/logging/ParentLoggersTest.java` has been observed failing intermittently - nut rarely - in the loom repo.
After inspection of the code Logger::doSetParent was found to do multiple read of the volatile `parent` field. After changing the method to do a single read the test has no longer been observed failing.

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Commit messages:
 - 8377457: java/util/logging/ParentLoggersTest.java failed intermittently

Changes: https://git.openjdk.org/jdk/pull/29634/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29634&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8377457
  Stats: 13 lines in 2 files changed: 6 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/29634.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29634/head:pull/29634

PR: https://git.openjdk.org/jdk/pull/29634