RFR: 8291418: adjust monitor deflation logging and deflate_idle_monitors use

[Daniel D. Daugherty]

Trivial fixes to monitor deflation logging and deflate_idle_monitors use.

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Commit messages:
 - 8291418: adjust monitor deflation logging and deflate_idle_monitors use

Changes: https://git.openjdk.org/jdk/pull/11293/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11293&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291418
  Stats: 13 lines in 2 files changed: 3 ins; 2 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/11293.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11293/head:pull/11293

PR: https://git.openjdk.org/jdk/pull/11293