Remove setalpha(0f) from reset.

Reset has too many callers for different reasons. It is extremely frail
and is causing the user switcher to disappear for various reasons.
Largely the user switcher disappears when switching users in the bouncer
and persisting the bouncer.

Fixes: 290355544
Test: Get multiple users and switch users with bouncer user switcher on.
Test: close and open bouncer scrimmed to see that the userswitcher does
not flicker.

Change-Id: I313240f1c594d5df6071b0dc6a7099496990e274