remove log of sensitive data

[markdboyd]

Changes proposed in this pull request:

• the Settings struct contains AWS key information: https://github.com/cloud-gov/cf-cdn-service-broker/blob/42e47a9371fd070b37f3d6575bd87d92b473f1f5/config/config.go#L20-L22, so removing the line that it includes it in logs

security considerations

This change removes code that was logging sensitive information to the output