RFR: CODETOOLS-7902977: jcstress: Minor touchups for jcstress-samples

[Aleksey Shipilev]

Some post-review comments emerged for jcstress-samples, this should make them cleaner.

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Commit messages:
 - CODETOOLS-7902977: jcstress: Minor touchups for jcstress-samples
 - Editorial changes in samples

Changes: https://git.openjdk.java.net/jcstress/pull/80/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=80&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902977
  Stats: 604 lines in 13 files changed: 281 ins; 286 del; 37 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/80.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/80/head:pull/80

PR: https://git.openjdk.java.net/jcstress/pull/80