Integrated: JDK-8312115: GenShen: fix log messages

[Kelvin Nilsen]

This PR addresses observed shortcoming in GC log messages for bootstrap GCs

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Commit messages:
 - Fix whitespace
 - Merge remote-tracking branch 'origin/master' into fix-bootstrap-logs
 - Merge remote-tracking branch 'origin/master' into fix-bootstrap-logs
 - Merge remote-tracking branch 'origin/master' into fix-bootstrap-logs
 - Merge remote-tracking branch 'origin/master' into fix-bootstrap-logs-gh
 - Fix handling of Concurrent GLOBAL cycles
 - Fix bootstrap log messages

Changes: https://git.openjdk.org/shenandoah/pull/319/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=319&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312115
  Stats: 28 lines in 4 files changed: 15 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/shenandoah/pull/319.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/319/head:pull/319

PR: https://git.openjdk.org/shenandoah/pull/319