RFR (S) 8244226: Shenandoah: per-cycle statistics contain worker data from previous cycles

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8244226

See how it fails in the bug.

Fix:
  https://cr.openjdk.java.net/~shade/8244226/webrev.01/

Testing: hotspot_gc_shenandoah {fastdebug,release}, eyeballing gc logs

-- 
Thanks,
-Aleksey