This bug does actually break certain farms

how to reproduce:
1. start game in creative
2. create the set up shown in the screenshot

3. stand where the armor stand is

4. go into survival

5. wait for skeleton to shoot the witch

6. go back into creative

7. place creeper in cell with witch

8. wait for it to be hit with a poison potion

9. notice how it doesn't agro on the witch

sceenshot of set up
https://cdn.discordapp.com/attachments/435875101360259074/526235256064311319/2018-12-22_21.04.43.png