Updated the namespace for environment.

It is execption when try to update envirnment options.

```
 $ ebfly env update web -a docker -o environment-RDS_DB_NAME=rds_db_name
 ERR! Configuration validation exception: Invalid parameter value (Namespace: 'aws:elasticbeanstalk:environment', OptionName: 'RDS_DB_NAME'): Unknown configuration setting.
```