[14] RFR 8237392: Shenandoah: Remove unreliable assertion

[Zhengyu Gu]

Offline discussion concluded that the assertion added by JDK-8237369 is 
not reliable.

For piggyback reference updating cycle, has_forwarded_objects flag is 
carried into next GC cycle and Shenandoah resets marking bitmap 
concurrently just before new GC cycle. So, there is a short period 
without reliable marking bitmap, could trigger false assertion.


Bug: https://bugs.openjdk.java.net/browse/JDK-8237392
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8237392/webrev.00/

Test:
   hotspot_gc_shenandoah

Thanks,

-Zhengyu