Wait a while before canceling the notification If the notification in the enqueued list that hasn't had a chance to post yet, the cancel operation will not really do until it posted. Wait for the notification to be posted before canceling it. Bug: 160446933 Test: run cts -m CtsAppTestCases -t android.app.cts.NotificationManagerTest#testCancel Change-Id: I7a80410eac1a8b5497d7aa71e78a2ce90a7a9455