Background: You have configured mongodb for replication, uncomment replication and added the line: replSetName: name_for_your_set.
You restart the service, check the status and everything is ok.
You start the client and try to create user, the above error is displayed.
Solution: Comment both the lines replication and replSetName in your configuration file , save the file and restart the service.
Start the client and add the user.
Remember to switch back the configuration and restart the service.