RFR: CODETOOLS-7902873: jcstress: Clean up text reporting

[Aleksey Shipilev]

We can make the output a little bit better.

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Commit messages:
 - CODETOOLS-7902873: jcstress: Clean up text reporting

Changes: https://git.openjdk.java.net/jcstress/pull/23/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=23&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902873
  Stats: 54 lines in 5 files changed: 28 ins; 10 del; 16 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/23.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/23/head:pull/23

PR: https://git.openjdk.java.net/jcstress/pull/23