Prevent displaying duplicated guest notifications.

Bug: 333677801
Test: atest GuestUserInteractorTest#registersBroadcastReceiversOnlyForSystemUser
Test: Manually switch to guest user while at least one secondary user
      was running either in background or foreground,
      and verify there are no duplicated notifications.
Flag: None
Change-Id: I4ea487bb6dbcfec136c7c8dda77d0b3cde345164