Check tiller_enabled when cern chart is enabled

https://its.cern.ch/jira/browse/OS-14392

magnum/drivers/common/templates/kubernetes/helm/cern-chart.sh

@@ -147,6 +147,13 @@ EOF
 fi
 
 if [ "$(echo ${CERN_CHART_ENABLED} | tr '[:upper:]' '[:lower:]')" = "true" ]; then
+
+    # if tiller_enabled is not true catch error
+    if [ "$(echo ${TILLER_ENABLED} | tr '[:upper:]' '[:lower:]')" != "true" ]; then
+        echo "ERROR: 'TILLER_ENABLED' must be true when 'cern_chart' is enabled, current value: " + ${TILLER_ENABLED}
+        exit 1
+    fi
+
     HELM_MODULE_CONFIG_FILE="/srv/magnum/kubernetes/helm/${CHART_NAME}.yaml"
     [ -f ${HELM_MODULE_CONFIG_FILE} ] || {
         echo "Writing File: ${HELM_MODULE_CONFIG_FILE}"