isolated_app: grant append on app_data_file

am: 4e6655b5

Change-Id: I13896b6e919f8bd10573aa085bf73998e28f8661

isolated_app.te

@@ -13,7 +13,7 @@ type isolated_app, domain;
 app_domain(isolated_app)
 
 # Access already open app data files received over Binder or local socket IPC.
-allow isolated_app app_data_file:file { read write getattr lock };
+allow isolated_app app_data_file:file { append read write getattr lock };
 
 allow isolated_app activity_service:service_manager find;
 allow isolated_app display_service:service_manager find;