RFR: 8300267: Remove duplicated setter/getter for do_not_unlock

[Robbin Ehn]

Hi please consider.

Testing t1 + zero build

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Commit messages:
 - Fixed

Changes: https://git.openjdk.org/jdk/pull/12044/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12044&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300267
  Stats: 9 lines in 2 files changed: 0 ins; 4 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/12044.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12044/head:pull/12044

PR: https://git.openjdk.org/jdk/pull/12044