hg: shenandoah/jdk10: Stop string dedup thread during VM shutdown

[zgu at redhat.com]

Changeset: 9e4135b88ace
Author:    zgu
Date:      2017-10-31 13:08 -0400
URL:       http://hg.openjdk.java.net/shenandoah/jdk10/rev/9e4135b88ace

Stop string dedup thread during VM shutdown

! src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp