Add "Intent.FLAG_ACTIVITY_CLEAR_TOP" flag in test.

The "Intent.FLAG_ACTIVITY_CLEAR_TOP" should be added in the intent for switching modes. This flag
ensures there is only 1 instance of the same activity. This behavior is the same as how we do in the
app.

bug:5336037
Change-Id: Ie76b43cbd87ff9e8a7ec9e0a892930834dccf9cf
1 file changed