Add test_delete_old_cwb_img()
Add test_delete_old_cwb_img()

chenyang14/electronic-blackboard,SWLBot/electronic-blackboard,Billy4195/electronic-blackboard,chenyang14/electronic-blackboard,Billy4195/electronic-blackboard,SWLBot/electronic-blackboard,stvreumi/electronic-blackboard,Billy4195/electronic-blackboard,stvreumi/electronic-blackboard,SWLBot/electronic-blackboard,SWLBot/electronic-blackboard,chenyang14/electronic-blackboard,stvreumi/electronic-blackboard,stvreumi/electronic-blackboard,Billy4195/electronic-blackboard