Fixed calls to onUserVisibilityChanged() for system user.

When the system user is switched out, it should call
SystemServiceManager.onUserVisibilityChanged(0, false), but it was instead
calling SystemServiceManager.onUserStarting(0, false).

Test: manual verification
Test: atest FrameworksServicesTests:UserControllerTest

Fixes: 255895655
Bug: 244333150

Change-Id: Ib15d89b77b9ff247e9d92411cf806f74c6aa0b3c