✨ Set cluster name in the OCCM

[michal-gubricky]

What this PR does / why we need it:
This PR sets the cluster name in the OCCM to make the name for the ingress-nginx load balancer unique

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes SovereignCloudStack/k8s-cluster-api-provider#495

Tested with the cluster name set to cs-cluster:

k describe po openstack-cloud-controller-manager-9l724 -n kube-system --kubeconfig cs-cluster.kubeconfig
Containers:
  openstack-cloud-controller-manager:    
    Environment:
      CLOUD_CONFIG:  /etc/config/cloud.conf
      CLUSTER_NAME:  cs-cluster

After the installation of Ingress-NGINX, the load balancer was created in the gx-scs with the expected name, see attached pic.

[chess-knight]

LGTM