RFR: [11, 10, 8]: Disable evac assist by default until bugfixes arrive

[Aleksey Shipilev]

Testing discovered the intermittent bug in evac assist code. I have a bugfix for sh/jdk, currently
in stress testing. Until we get another bunch of backports integrated, it makes sense to disable it
in backport repos. I am going to do this in all backports at once.

diff -r af8ae6c1be4e src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp
--- a/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp    Wed Aug 22 23:17:47 2018 +0200
+++ b/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp    Thu Aug 23 18:14:56 2018 +0200
@@ -100,5 +100,5 @@
           "concurrent evacuation. Possible values: 'on', 'off', 'adaptive'")\
                                                                             \
-  experimental(uintx, ShenandoahEvacAssist, 10,                             \
+  experimental(uintx, ShenandoahEvacAssist, 0,                              \
           "How many objects to evacuate on WB assist path. "                \
           "Use zero to disable.")                                           \

Testing: misbehaving tests

Thanks,
-Aleksey