Fix Select mode problem with animation off

- Avoid calling resetTaskVisuals when entering Modal state with animation off, it should only be called when leaving Overview, to be consistent with animation on case
- Use a separate property to control alpha for modalness, to avoid being overridden by other transition

Fix: 320314839
Test: presubmit
Flag: ACONFIG com.android.launcher3.enable_overview_icon_menu TEAMFOOD
Change-Id: I12a35682e25c3a70bc263afdc90a7895d6c56f11