Disable blurs while in multiwindow mode

- With hierarchical animations, the split-secondary shell root
  is moved above the split-primary shell root immediately during
  transitions, which means that setting the blur on the launcher
  surface will also affect the primary docked surface

Bug: 154125518
Change-Id: I21dd01738ee9bc974d41e5964364917a30143a2a
5 files changed