Entities receive knockback from splash potions based on the direction that the said entity was facing when throwing the potion

When a player is harmed by a potion, they get knock back in the direction away from the player that threw it, rather than from the point the potion breaks, which doesn't make sense as it pulls the player toward the break point when the opposite should happen.

Steps to reproduce:

1. Load a world with 2 players, one being in survival
2. Get a potion of harming in one player and splash it in differing locations around the other player. Notice how the affected player is knocked away from the other player, rather than the point of the splash.