Llamas don't leave their caravan when being leashed by a player

When a player attaches a lead to a llama that is part of a caravan, and tries to lead that llama somewhere else, that llama won't leave the caravan.

To reproduce

Using MC-205200:

1. Leash a llama onto a fence
2. Spawn a llama next to it
3. Leash that llama
4. Walk away from the fence
   → The llama will try to get back to the fence, and at some point the lead will pop off

With multiple llamas:

1. Spawn multiple llamas
2. Attach a lead to one of them
3. Walk a bit
   → The llamas form a caravan
4. Attach a lead to the last llama in the caravan
5. Walk a bit
   → The last llama walks backwards and tries to follow the second-to-last llama in the first caravan

Videos

• 20w46a:
  • with fence: Minecraft 20w46a - Singleplayer 2020-11-11 21-26-21.mp4
  • with multiple llamas: Minecraft 20w46a - Singleplayer 2020-11-11 21-33-46.mp4
• 1.16.x (modded): https://youtu.be/I0aWgN54nzs?t=1207