Fix iterator test

Author: ngallagher

snap-common/src/test/java/org/snapscript/common/CompoundIteratorTest.java

@@ -3,6 +3,7 @@
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.Iterator;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -11,7 +12,7 @@
 public class CompoundIteratorTest extends TestCase {
 
    public void testIterator() {
-      Set<String> one = new HashSet<String>();
+      Set<String> one = new LinkedHashSet<String>();
       List<String> two = new ArrayList<String>();
       List<String> three = new ArrayList<String>();