Improvements to IndexPopulationStressTest

- Parameterized instead of subclassed
- Broke out some code to methods
- Uses SimpleNodeValueClient instead of a modified NodeValueIterator
- Simplified random value generator a bit

community/kernel/src/main/java/org/neo4j/kernel/impl/index/schema/NodeValueIterator.java

@@ -37,8 +37,6 @@ public class NodeValueIterator extends PrimitiveLongCollections.PrimitiveLongBas
 {
     private boolean closed;
     private IndexProgressor progressor;
-    private boolean needsValues;
-    private Value[] values;
 
     @Override
     protected boolean fetchNext()
@@ -61,25 +59,18 @@ public void initialize( IndexDescriptor descriptor,
                             boolean needsValues )
     {
         this.progressor = progressor;
-        this.needsValues = needsValues;
     }
 
     @Override
     public boolean acceptNode( long reference, Value... values )
     {
-        this.values = values;
         return next( reference );
     }
 
-    public Value[] getValues()
-    {
-        return values;
-    }
-
     @Override
     public boolean needsValues()
     {
-        return needsValues;
+        return false;
     }
 
     @Override