hg: shenandoah/jdk: Fix single-threaded reference processing

[roman at kennke.org]

Changeset: b9c9c7859531
Author:    rkennke
Date:      2018-07-20 15:10 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/b9c9c7859531

Fix single-threaded reference processing

! src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
! src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
! src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
! src/hotspot/share/gc/shenandoah/shenandoahWorkGroup.cpp
! src/hotspot/share/gc/shenandoah/shenandoahWorkGroup.hpp