RFR: Backout: Only put regions with objects into traversal set

[Roman Kennke]

Yesterday's innocent looking change seems to cause failures. Let's back
it out. Ok?

# HG changeset patch
# User rkennke
# Date 1529072381 -7200
#      Fri Jun 15 16:19:41 2018 +0200
# Node ID de16edd34c6dbfbaea63ddf2dabc43171c1cada7
# Parent  39c89fe71702f0aff16e2457615b9b65613458d6
Backout: Only put regions with objects into traversal set

diff --git
a/src/hotspot/share/gc/shenandoah/heuristics/shenandoahTraversalHeuristics.cpp
b/src/hotspot/share/gc/shenandoah/heuristics/shenandoahTraversalHeuristics.cpp
---
a/src/hotspot/share/gc/shenandoah/heuristics/shenandoahTraversalHeuristics.cpp
+++
b/src/hotspot/share/gc/shenandoah/heuristics/shenandoahTraversalHeuristics.cpp
@@ -83,9 +83,9 @@
       if (garbage_percent > ShenandoahGarbageThreshold) {
         collection_set->add_region(r);
       }
-      traversal_set->add_region(r);
     }
     r->clear_live_data();
+    traversal_set->add_region(r);
   }
   collection_set->update_region_status();
 }