If the notification shade was swiped down, the activity that
this test wants to verify will be behind the notification
shade, and this causes the test failed. Thus, this change
makes the screen back to home before starting the test to
avoid the activity being hidden by the notification shade.
Bug: 240891836
Test: NetworkNotificationManagerTest#testNotifyNoInternetAsDialogWhenHighPriority
Change-Id: I4d903d2623c462fca4ec07eb0a0231ef527a200b
7fcbc2ecbd