Disable the guest user completely in El Capitan without having to disable 'Find My Mac' I know it should be straight forward but unfortunately, it  isn't.

I did disable the guest user in the System Preferences by unchecking the checkbox for Allow guests to login in to this computer, but it still shows up on the login screen.

I have heard that disabling 'Find My Mac' would fix it for OS X Lion, but I want to keep it.

Is there a way to do this?
@alan-shutko pointed out very important info about this in his comment:


  The point is to make Find My Mac work. If you turn Find My Mac off,
  the guest account will go away. The reason it's there if Find My Mac
  is on is that if someone steals your mac, it cannot report its
  position unless the thief connects it to a wifi network.


Looks like we should keep it on.