hg: shenandoah/jdk11: Disable evac assist by default until bugfixes arrive

[shade at redhat.com]

Changeset: 1ac17269e542
Author:    shade
Date:      2018-08-23 18:15 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk11/rev/1ac17269e542

Disable evac assist by default until bugfixes arrive

! src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp