Fixing keyguard user switcher height after collapsing

User switcher still had expanded flight after being collapsed - caused by all children views (of type KeyguardUserDetailItemView) still being visible but having alpha of 0.
The function to make them GONE was called too early and with improper value, so they were never GONE.
Fix is to make them VISIBLE before animating opening user switcher and make them GONE only after closing animation is finished.

Fixes: 210121179
Test: open keyguard user switcher and close it -> views below should move back to their previous positions
Change-Id: I76ea8651b19ef7ae931e6c14951d804a85c237ed