Passive mobs used to stop running away from you after few seconds when you've hit them, but now they run away forever untill the world is reloaded.
I don't know about multiplayer, but this is definitely on singleplayer.

Steps to reproduce:
1. Spawn or find a passive mob
2. hit it once
3. Observe that it runs away from you forever
4. hold their specific food (I mean, for pig, hold a carrot)
5. Observe they don't care
6. Quit and rejoin the world
7. Observe that they are back to normal and will follow their specific food.