Removes sensitive strings from config when printing
Removes sensitive strings from config when printing

Towards https://github.com/giantswarm/aws-operator/issues/159

When we print the entire config struct, this includes some
sensitive fields, such as the AWS access key secret.
We don't want this leaking out, and being picked up by logging
infrastructure, for example.
This changeset adds a String method to Config, which redacts
the sensitive fields before printing.

kinvolk/aws-operator,giantswarm/aws-operator,giantswarm/aws-operator