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"