Revert^2 "[flexiglass] Fixes issue where user management settings didn't show"

This reverts commit 58fa809b.

Reason for revert: redoing the original but fixing the compile error.

Fix: 366282915
Test: unit test added. It fails withoug the fix and succeeds with it
Test: manually verified the mentioned user flow with SWIPE and with
PATTERN to make sure it always works right
Flag: com.android.systemui.scene_container

Change-Id: I1c91055c9cf058949b8856c53600c5c876c02228