Do not collapse the shade when clicking the last notification.

This CL prevents the shade from collapsing as soon as the user clicks a
notification which is auto-cancelled and was the last one shown. The
shade will still collapse, but at the end of the notification animation.

Bug: 181654098
Test: Manual
Change-Id: Ieb0e1005c8e096a53b97dd402fa4ef26cb38c7bf