Avoid smooth scrolling tab changes when the app is not open

Bug: 26778694

There can be a tug-of-war between the activity transition as
DeskClock is opened (by tapping on the clock widget) and the
change of tabs if the clock tab was not the selected tab.

Change-Id: I3aa17aedc1d5c78d16c3feee4e70935b5547d254