Switch some recent tasks calls from IATM to ATM

The aidl IActivityTaskManager interface doesn't allow for method
overloading with the same name. Switching some of these calls to use
ActivityTaskManager class instead makes it easier to have overloads in
upcoming CLs.

Test: they pass!
Bug: 172776536
Change-Id: Ic4895ccf7dc1207cc6b14004cfcf6ee7b4b76cc1