Fix side button visibility tracking.

Previously one could e.g. get legacy menu button being visible in
certain scenarios, like this one:
- Open legacy app, e.g. CatLog
- Invoke IME
- Lock screen
- Unlock screen
- Result: Menu button visible in keyguard

Change-Id: Ia796f73ec995ea1cc34d38f8aefdbccda7be7565
Merge "Fix side button visibility tracking." into du44