RFR: JDK-8301637: Fixed bug that regressed TLR.doubles()

[kabutz]

ThreadLocalRandom.current().doubles().parallel() had a bad regression, because it called the superclass methods of the ThreadLocalRandomProxy's nextDouble() method instead of delegating to the ThreadLocalRandom.current().

Affects all versions of ThreadLocalRandom since Java 17.

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Commit messages:
 - Fixed bug that regressed TLR.doubles()

Changes: https://git.openjdk.org/jdk/pull/12366/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12366&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301637
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/12366.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12366/head:pull/12366

PR: https://git.openjdk.org/jdk/pull/12366