Cluster-image-registry-operator: exposes a secret via env variable in pod definition on azure

An information disclosure flaw was found in OpenShift's internal image registry operator. The AZURE_CLIENT_SECRET can be exposed through an environment variable defined in the pod definition, but is limited to Azure environments. An attacker controlling an account that has high enough permissions to obtain pod information from the openshift-image-registry namespace could use this obtained client secret to perform actions as the registry operator's Azure service account.