[14] RFR 8246097: Shenandoah: limit parallelism in CLDG root handling

[Aleksey Shipilev]

Original RFE:
  https://bugs.openjdk.java.net/browse/JDK-8246097
  https://hg.openjdk.java.net/jdk/jdk/rev/c60f06714a9e

The context in 14u is a bit different. Trivial application of the rejected hunks by hand.
  http://cr.openjdk.java.net/~shade/8246097/webrev.14u.01/

Testing: hotspot_gc_shenandoah, tier{1,2} with Shenandoah enabled

-- 
Thanks,
-Aleksey