Make sure to stop noHistory="true" activities properly

The code was correctly inducing a 'finish' when such an activity was
being stopped, but then was not continuing with the rest of the stop
bookkeeping at that point.  In some circumstances this could result
in an inconsistent state, with the activity marked as finishing but
neither in the foreground nor stopped.

Bug 6585403

Change-Id: Ib5c5be885bc6534e099e040d87a8589f7b7454ce