Also consider task intent when trimming recent tasks

7cbfcd88 we stopped comparing
the tasks realActivity when trimming recent task. This led to
task with the same intent been duplicated in the recents list.
We now consider the task intent when deciding when to trim like
we did pre 510e5542.

Bug: 22812470
Bug: 22564474
Bug: 18642190
Change-Id: I90b3ab9cf7a06b4691099f697e723d8a54def9fa