Cleanup whole preloads directory

When leaving SUW, cleanup preloads directory, not just demo dir.

Bug: 29908713
Change-Id: Id94e6df619f5ca6585b2a0edb0f1028364431f95
diff --git a/services/retaildemo/java/com/android/server/retaildemo/RetailDemoModeService.java b/services/retaildemo/java/com/android/server/retaildemo/RetailDemoModeService.java
index a92498b..855a2b6 100644
--- a/services/retaildemo/java/com/android/server/retaildemo/RetailDemoModeService.java
+++ b/services/retaildemo/java/com/android/server/retaildemo/RetailDemoModeService.java
@@ -231,8 +231,8 @@
                 BackgroundThread.getHandler().post(new Runnable() {
                     @Override
                     public void run() {
-                        if (!deleteDemoFolderContents()) {
-                            Slog.w(TAG, "Failed to delete demo folder contents");
+                        if (!deletePreloadsFolderContents()) {
+                            Slog.w(TAG, "Failed to delete preloads folder contents");
                         }
                     }
                 });
@@ -388,8 +388,8 @@
                 getContext().getContentResolver(), Settings.Global.DEVICE_PROVISIONED, 0) != 0;
     }
 
-    private boolean deleteDemoFolderContents() {
-        final File dir = Environment.getDataPreloadsDemoDirectory();
+    private boolean deletePreloadsFolderContents() {
+        final File dir = Environment.getDataPreloadsDirectory();
         Slog.i(TAG, "Deleting contents of " + dir);
         return FileUtils.deleteContents(dir);
     }