Fix magnum cern-chart.sh usage of bash commands `$()` on _cern_chart_values_file

The parts that must be removed are:

[...]
    landb-sync:
      landbSet:
        enabled: $(if [ "$LANDB_SYNC_SET" != "" ]; then echo "true"; else echo "false"; fi) <~~ usage of bash command
[...]
    openstack-cloud-controller-manager:
      extraInitContainers:
      - name: init-waitkeystone
        command: ["sh", "-c", "until nslookup $(echo ${AUTH_URL} | cut -d'/' -f3); do echo waiting for keystone; sleep 2; done;"] <~~ usage of bash command
[...]
    kube-prometheus-stack:
      prometheus:
        prometheusSpec:
          resources:
            requests:
              cpu: $(expr 128 + 7 \* ${MAX_NODE_COUNT} )m <~~ usage of bash command
              memory: $(expr 256 + 40 \* ${MAX_NODE_COUNT})M <~~ usage of bash command
[...]