Always create root task for ACTIVITY_TYPE_RECENTS

- When alwaysCreateRootTask() returns false lets say for recents
  activity, it leads to double nesting of root tasks on top of recents.
- This double nesting works fine for phones where recents is
  full-screen but it leads to inconsistent state for the cases where
  the recents activity itself needs to be in a multi window mode i.e.
  inside a launch root task.

Fix: 277088827
Test: atest TaskDisplayAreaTests
Change-Id: I3a097028b58b451a33932eb039ae9fb970d734df