Llamas have unused saddle slot

Steps to reproduce:

• Spawn a llama
• Using the following command will put a saddle where the horse saddle goes

  /replaceitem entity @e[type=llama,c=1] slot.horse.saddle saddle
  

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As of 16w39b:
It still sets the item as SaddleItem value. This field should probably not exist for llamas.