Mob AI stops on pointed dripstone.

 When mobs walk into a pointed dripstone block they stop moving.

What I expected to happen was...: 

Mobs move around the pointed dripstone.

What actually happened was...:
 Mobs freeze when inside a pointed dripstone.

Steps to Reproduce:
1. Mob tracks player.
2. Walks into pointed dripstone.
3. Gets stuck there until player moves.