RFR (S): All threads should have GC LABs

[Aleksey Shipilev]

Hi,

We had a curious failure where VMThread invoked the biased locking rebiasing,
which stored the header into mark word on one of the object, which took a write
barrier, which discovered that we need to evacuate the object first, which
failed because VMThread has no GC LABs available to evacuate to.

This fixes it by providing all threads with GC LABs:
  http://cr.openjdk.java.net/~shade/shenandoah/all-threads-gclab/webrev.01/

Testing: hotspot_gc_shenandoah, jcstress -m quick

Thanks,
-Aleksey