Use helm upgrade instead of install

This allows to skip the helm install error:

helm -n kube-system install cern-magnum releases/cern-magnum --wait --version 0.11.0 --values /opt/magnum/install-cern-magnum-values.yaml
Error: cannot re-use a name that is still in use

Installation of the CERN helm chart occurs when cluster is created. https://gitlab.cern.ch/kubernetes/magnum/-/blob/cern/train/magnum/drivers/k8s_fedora_coreos_v1/templates/kubecluster.yaml#L1510 After a while if the job dosen't finish (due to heavy load on master node) the cern-metachart job will create a new install pod. There is a chance that a new chart installation might be tried while there is a chart mid installation. So the release exists but is not complete. By using helm install installations that might end up being successfull will fail subsequently, while helm upgrade will 'upgrade' and pick up any leftover to-dos.

Change-Id: I2c18624e343d109891b9d19b67b4961e917ebe37