RFR (XS) 8232802: Shenandoah: transition between "cset" and "pinned_cset" does not require cancelled gc

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8232802

Fix:
  https://cr.openjdk.java.net/~shade/8232802/webrev.01/

The failure caught in testing says that transition from cset to pinned-cset is invalid when GC was
not cancelled. However, this was only true before JDK-8232575 work. Now, this transition is done in
sync_pinned_region_status that is supposed to work on all paths. In this case, Degenerated GC
dropped the cancelled GC flag already, and thus blows up the check.

The check is excessive and should be removed.

Testing: hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey