Disable KQS flatenning for some WMShell unit tests

- The behavior with KQS flatenning ON is already verified with unit
  tests. So, we don't need to add different variant of tests for failing
  tests.
- So only disable the flag for the unit tests that are failing as these
  tests are expecting X heirarchy changes but are getting Y with KQS
  flatenning flag ON.

Fix: 413074928
Bug: 382769617
Test: atest WMShellUnitTests:DesktopTasksControllerTest
Flag: EXEMPT disabling flag for unit tests
Change-Id: I05c87462d0e50e9e3e6d98ed1b6b1cd94769faf1