/kind bug

What happened:
I wanted to use my clouds.yaml for authentication, but the options are never used by the kms plugin

What you expected to happen:
Authenticate like with OCCM.

How to reproduce it:
Try to use the clouds.yaml authentication method.

Anything else we need to know?:
https://github.com/kubernetes/cloud-provider-openstack/blob/master/pkg/kms/barbican/barbican.go#L28-L38