Disable camera's lockscreen shortcut
I'm not aware of any native settings for this, but there is an app that was built to bridge the gap: Lockscreen Policy. When you first launch it, you'll need to hit the "Activate" button to give it device administration permission, then you simply toggle the camera to "Off":



One caveat to this app that the author notes on the Google Play page:


  Does not work on TouchWiz Android 4.2.x firmware (such as Galaxy S4)


However, this does not apply in your case, since the N4 is not running TouchWiz.