`OS_CLOUD` environment variable should be ignored

[stephenfin]

/kind bug

What steps did you take and what happened:

Users pass cloud credentials by placing a clouds.yaml in a Secret and configuring OpenStackClusterSpec.Cloud (for the cloud name) and OpenStackClusterSpec.IdentityRef. However, if OS_CLOUD is defined, we can end up with a mismash of clouds.

What did you expect to happen:

We should ignore environment variables. All configuration should be pulled from the Secret.

Anything else you would like to add:

none.

Environment:

• Cluster API Provider OpenStack version (Or git rev-parse HEAD if manually built): master
• Cluster-API version: n/a
• OpenStack version: n/a
• Minikube/KIND version: n/a
• Kubernetes version (use kubectl version): n/a
• OS (e.g. from /etc/os-release): n/a

[mdbooth]

This was fixed by #1883