RFR: Fullgc should honor aging cycle

[Kelvin Nilsen]

As previously implemented, Full GC always incremented object ages.  It should only increment object ages if this is an aging cycle.  This was detected during code review.  This is a correctness improvement without known performance implications.

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Commit messages:
 - Merge remote-tracking branch 'GitFarmBranch/full-gc-should-honor-aging-cycle' into fullgc-should-honor-aging-cycle
 - Full GC should only increment object age during aging cycles

Changes: https://git.openjdk.org/shenandoah/pull/212/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=212&range=00
  Stats: 9 lines in 2 files changed: 8 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/shenandoah/pull/212.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah pull/212/head:pull/212

PR: https://git.openjdk.org/shenandoah/pull/212