RFR: 7904043: jcstress: AdvancedJMM_15_VolatilesAreNotFences.Fences is failing after CODETOOLS-7904033

[Aleksey Shipilev]

In [CODETOOLS-7904033](https://bugs.openjdk.org/browse/CODETOOLS-7904033), I made a little mistake of rewriting Unsafe.storeFence to VarHandle.acquireFence. It should be VarHandle.releaseFence. That subtest is currently failing on AArch64.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jcstress/pull/173/files
  Webrev: https://webrevs.openjdk.org/?repo=jcstress&pr=173&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904043
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jcstress/pull/173.diff
  Fetch: git fetch https://git.openjdk.org/jcstress.git pull/173/head:pull/173

PR: https://git.openjdk.org/jcstress/pull/173