Seagrass, kelp, coral and coral fans become waterlogged when placed in downwards flowing water

They should only become waterlogged when placed inside a water source block. To reproduce:

1. Dig a 1x1 two deep hole
2. Place a water source block on the top air block
3. Place a coral on the bottom
4. Remove the water source block from the top

Code Analysis:
Code analysis by JingyBreadMan can be found in this comment.