Zombie Pigmen become aggressive towards the player if they defeat a Villager-spawned Iron Golem that had previously provoked them

What I expected to happen was...:
Once the Zombie Pigmen kill the Iron Golem, they become neutral again because they defeated the mob that provoked them.

What actually happened was...:
Once the Zombie pigmen killed the Iron Golem, they continued to be aggressive and attacked me (the player).

Steps to Reproduce:
1. Find or create a village
2. Let the villagers summon an Iron Golem
3. Summon as many Zombie Pigmen as necessary for them to take down the Iron Golem
4. Let the Zombie Pigmen defeat the golem
5. The Zombie Pigmen will continue to be agressive and start attacking the player.