RFR: 8351992: JFR: Improve robustness of the SettingControl examples

[Erik Gahlin]

Could I have a review of PR that improves the robustness of the SettingControl examples.

Testing: jdk/jdk/jfr + tier1

Thanks
Erik

-------------

Commit messages:
 - Minor changes
 - Initial

Changes: https://git.openjdk.org/jdk/pull/24056/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24056&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351992
  Stats: 42 lines in 2 files changed: 31 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/24056.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24056/head:pull/24056

PR: https://git.openjdk.org/jdk/pull/24056