What is happening: When a mob is hit with the fire aspect enchantment  or walks into fire in the rain, the fire does not get extinguished.

What is expected to happen: When a mob is hit with the fire aspect enchantmentr walks into fire in the rain, the rain is expected to extinguish the fire from the mob in question.

How to reproduce this bug:

1. Toggle downfall in the world.
2. Get flint and steel.
3. Interact with the flint and steel on the ground. 
4. Spawn a mob like a zombie for example.