Fix test after MockToken refactor

MockToken class was extracted from DesktopModeControllerTest. But
conflicting changes landed which broke the build and the changes were
reverted. Applying the changes again by reverting the revert and fixing
the test.

Bug: 260645044,261234251,260645044
Test: atest DesktopModeControllerTest DesktopTasksControllerTest
Change-Id: I95f66c35c671e774c3a4f7ba6b64167595f69b60