RFR: 8288663: JFR: Disabling the JfrThreadSampler commits only a partially disabled state

[Markus Grönlund]

Greetings,

please review the following change set.

The problematic situation is described in the JIRA issue.

In addition, I have taken the opportunity to align "interval" with "period", since the concept is exported and used more pervasively.

Testing: jdk_jfr

Thanks
Markus

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Commit messages:
 - typo
 - 8288663

Changes: https://git.openjdk.org/jdk/pull/9199/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9199&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288663
  Stats: 123 lines in 7 files changed: 47 ins; 19 del; 57 mod
  Patch: https://git.openjdk.org/jdk/pull/9199.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9199/head:pull/9199

PR: https://git.openjdk.org/jdk/pull/9199