[gen/reference-api] Set 'exotic=no' at cluster level if not specified in input yaml

data/grid5000/sites/grenoble/clusters/dahu/dahu.json

 {
   "created_at": "Thu, 22 Mar 2018 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/grenoble/clusters/troll/troll.json

 {
   "created_at": "Mon, 23 Dec 2019 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/grenoble/clusters/yeti/yeti.json

 {
   "created_at": "Tue, 16 Jan 2018 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lille/clusters/chetemi/chetemi.json

 {
   "created_at": "Thu, 01 Dec 2016 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lille/clusters/chiclet/chiclet.json

 {
   "created_at": "Mon, 06 Aug 2018 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lille/clusters/chifflet/chifflet.json

 {
   "created_at": "Thu, 01 Dec 2016 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lille/clusters/chifflot/chifflot.json

 {
   "created_at": "Wed, 01 Aug 2018 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/luxembourg/clusters/granduc/granduc.json

 {
   "created_at": "Thu, 01 Dec 2011 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/luxembourg/clusters/petitprince/petitprince.json

 {
   "created_at": "Tue, 10 Sep 2013 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lyon/clusters/gemini/gemini.json

 {
   "created_at": "Sun, 01 Sep 2019 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lyon/clusters/hercule/hercule.json

 {
   "created_at": "Tue, 02 Oct 2012 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lyon/clusters/nova/nova.json

 {
   "created_at": "Thu, 01 Dec 2016 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lyon/clusters/orion/orion.json

 {
   "created_at": "Fri, 14 Sep 2012 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lyon/clusters/sagittaire/sagittaire.json

 {
   "created_at": "Sat, 01 Jul 2006 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/lyon/clusters/taurus/taurus.json

 {
   "created_at": "Fri, 14 Sep 2012 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/nancy/clusters/graffiti/graffiti.json

 {
   "created_at": "Fri, 07 Jun 2019 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/nancy/clusters/graoully/graoully.json

 {
   "created_at": "Mon, 04 Jan 2016 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/nancy/clusters/graphique/graphique.json

 {
   "created_at": "Tue, 12 May 2015 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/nancy/clusters/graphite/graphite.json

 {
   "created_at": "Thu, 05 Dec 2013 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {

data/grid5000/sites/nancy/clusters/grcinq/grcinq.json

 {
   "created_at": "Tue, 09 Apr 2013 00:00:00 GMT",
+  "exotic": false,
   "kavlan": true,
   "metrics": [
     {