hg: shenandoah/jdk: Cherry-pick: 8221278: Shenandoah should not enqueue string dedup candidates during root scan

[roman at kennke.org]

Changeset: b7e14f52d050
Author:    rkennke
Date:      2019-03-21 22:10 +0100
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/b7e14f52d050

Cherry-pick: 8221278: Shenandoah should not enqueue string dedup candidates during root scan

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