StatusBar: Make sure showKeyguard is called when needed

- Fixes an issue where the keyguard was not visible after returning
  from the bouncer because the panel was not expanded
- Fixes an issue where the keyguard was not hiding sensitive content
  because the showKeyguard call was made before the keyguard became
  locked
- Fixes an issue where the ambient display was showing bad state because
  the panel was not expanded when turning the screen off.

Test: trigger bouncer, press back. Observe that keyguard shows again. Also, trigger bouncer, then lock. Observe that ambient display works. Also turn on "hide sensitive notifications on lockscreen", observe that it actually does that.
Fixes: 37868130
Bug: 37907366
Change-Id: Ic03e46a067d6e6a0152796136c39a0de66301008