RFR: CODETOOLS-7902979: jcstress: Another round of samples updates

[Aleksey Shipilev]

These updates follow the recent JCStress Workshop and fix issues discovered there.

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Commit messages:
 - Fix some samples even more

Changes: https://git.openjdk.java.net/jcstress/pull/81/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=81&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902979
  Stats: 181 lines in 16 files changed: 83 ins; 33 del; 65 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/81.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/81/head:pull/81

PR: https://git.openjdk.java.net/jcstress/pull/81