Zone abstraction of object layer was returning `nil`
incorrectly under situations where disk healing is
not required. Returning `nil` is considered as healing
successful, which leads to unexpected ReloadFormat()
peer notification calls during startup.
This PR fixes this behavior properly for zones.
Maven repository requires HTTPS now. This lead to issues
building mint image in aws-sdk-java & minio-java.
The PR fixes the issue and also bump aws sdk version in
aws-sdk-java to the latest.
