Clients that join a server cannot create their own server once they leave the other server

The `.Disabled` property needs to be set back to false when the client leaves the other server.

Run `res://Framework/Netcode/Examples/TopDown/World.tscn` scene with `F6` to see the issue.

Creating this issue to try and get more people involved with this project. If no one gets to this then I'll eventually resolve it myself.