Disable selected windowing btns in HandleMenu

When the window is already in freeform, the freeform button should not
be clickable otherwise the task will re-attempt to enter freeform. Same
with the other windowing buttons / modes.

Flag: EXEMPT bug fix
Bug: 367976713
Test: enter desktop, press desktop button in handle menu, verify the
task doesn't move

Change-Id: Idbd9d13963f7eefa5b10a837cb9e8c2e438f8d12