Probably, you have some problems with your server’s configuration.
Follow these steps to remove and create a new one, it might help you.
In Eclipse
1. Window -> Show view -> Servers (If you cannot see it, you might need to choose Others -> Server)
2. From Server view -> Delete the server which has problems.
3. Right click -> New -> Server : to create a new one
In my case, after new server was created, I get rid of this “localhost-config is missing”