Fix nondeterminism in ListSetDifference

Test: Presubmits
Change-Id: Icafbe288810089f648a8a5051c3af45c61df3889
diff --git a/android/util.go b/android/util.go
index 30d8ec6..e8d9301 100644
--- a/android/util.go
+++ b/android/util.go
@@ -221,13 +221,13 @@
 	diff2 := []T{}
 	m1 := setFromList(l1)
 	m2 := setFromList(l2)
-	for t := range m1 {
+	for _, t := range l1 {
 		if _, ok := m2[t]; !ok {
 			diff1 = append(diff1, t)
 			listsDiffer = true
 		}
 	}
-	for t := range m2 {
+	for _, t := range l2 {
 		if _, ok := m1[t]; !ok {
 			diff2 = append(diff2, t)
 			listsDiffer = true