Nether portals only linking to one portal in multiplayer worlds

Put the summary of the bug you're having here

What I expected to happen was...:
The nether portal system would work as in previous versions, with new portals being made in the nether if far enough away in the overworld

What actually happened was...:
Every portal that any player made would exit into the nether in the same place. It would also link to the same portal once exiting the nether

Steps to Reproduce:
1. Make one nether portal
2. Make another portal a couple hundred blocks away
3. Both will sync to the same portal in the nether.