8191131: Nashorn test comparator breaks comparator contract

Reviewed-by: sundar, jlaskey

test/nashorn/src/jdk/nashorn/internal/test/framework/TestReorderInterceptor.java

@@ -47,6 +47,10 @@ public final class TestReorderInterceptor implements IMethodInterceptor {
                 final Object o2 = mi2.getInstance();
                 if (o1 instanceof ITest && o2 instanceof ITest) {
                     return ((ITest)o1).getTestName().compareTo(((ITest)o2).getTestName());
+                } else if (o1 instanceof ITest) {
+                    return 1;
+                } else if (o2 instanceof ITest) {
+                    return -1;
                 }
                 // something else, don't care about the order
                 return 0;