[MC-22972] Horses are stupid and walk into fire/lava/cacti.

What I expected to happen was...:
When I killed a squid, it should have dropped an ink sac.

What actually happened was...:
Horses won't walk into danger and try to commit suicide.

Steps to Reproduce:
1. Find a horse
2. Tame it
3. Leave it unleashed
4. Watch until it kills itself.