fix: fix CI with aritubee not define issue (#989)

diff --git a/molecule/shared/molecule.yml b/molecule/shared/molecule.yml
index ae3e563..fc4afdc 100644
--- a/molecule/shared/molecule.yml
+++ b/molecule/shared/molecule.yml
@@ -110,6 +110,9 @@
         keycloak_admin_password: secrete123
         # Monitoring
         kube_prometheus_stack_grafana_admin_password: secrete123
+        kube_prometheus_stack_prometheus_host: "prometheus.{{ domain_name }}"
+        kube_prometheus_stack_alertmanager_host: "alertmanager.{{ domain_name }}"
+        kube_prometheus_stack_grafana_host: "grafana.{{ domain_name }}"
         # Memcached
         openstack_helm_endpoints_memcached_secret_key: secrete123
         # RabbitMQ
diff --git a/roles/kube_prometheus_stack/defaults/main.yml b/roles/kube_prometheus_stack/defaults/main.yml
index 9882498..dfd4ee9 100644
--- a/roles/kube_prometheus_stack/defaults/main.yml
+++ b/roles/kube_prometheus_stack/defaults/main.yml
@@ -23,9 +23,9 @@
 
 kube_prometheus_stack_grafana_admin_password: "{{ undef('You must specify a Grafana password using kube_prometheus_stack_grafana_admin_password') }}"
 
-# kube_prometheus_stack_alertmanager_host:
-# kube_prometheus_stack_grafana_host:
-# kube_prometheus_stack_prometheus_host:
+kube_prometheus_stack_grafana_host: "{{ undef('You must specify a Grafana host using kube_prometheus_stack_grafana_host') }}"
+kube_prometheus_stack_alertmanager_host: "{{ undef('You must specify a Alertmanager host using kube_prometheus_stack_alertmanager_host') }}"
+kube_prometheus_stack_prometheus_host: "{{ undef('You must specify a Prometheus host using kube_prometheus_stack_prometheus_host') }}"
 
 kube_prometheus_stack_keycloak_server_url: "https://{{ keycloak_host }}"
 kube_prometheus_stack_keycloak_admin_realm_name: master