Put the summary of the bug you're having here

What I expected to happen was...:
I could hit the mob while its flying due to a hit

What actually happened was...:
When i hit the mob there was a small period of time i could not hit it again
(it was when it was being knocked back)

Steps to Reproduce:
1. Spawn something like a villager.
2. ...Hit it with a diamond sword
3. ...try to hit it again very quickly after that