Add more variables to settings

[garloff]

We have now hardcoded ovn provider loadbalancer twice.
Add more settings in cluster-settings[-template].env:

• loadbalancer in front of kubeapi (per cluster => CL_KUBEAPILB or so)
• default loadbalancer from CCM (per environment => CS_CCMLB or so)
• flavor type for control plane node (per cluster => CL_ )
• flavor type for worker nodes (per cluster)
• disk size for control plane node (only use when you use diskless flavor)
• disk size for worker node (only use when you use diskless flavor)

This will then also overcome the limitation from #2