add healthcheck when basic auth is configured

Author: ntk148v

ansible/roles/haproxy/templates/haproxy.cfg.j2

@@ -37,6 +37,12 @@ listen prometheus
 {% if enable_alertmanager | bool %}
 listen alertmanager
   bind {{ ansitheus_vip_address }}:{{ alertmanager_port }}
+  option httpchk GET /-/ready
+{% if alertmanager_web_config is defined and alertmanager_web_config.basic_auth_users | length > 0 %}
+  http-check expect status 401
+{% else %}
+  http-check expect status 200
+{% endif %}
   http-request del-header X-Forwarded-Proto
   http-request set-header X-Forwarded-Proto https if { ssl_fc }
 {% for host in groups['alertmanager'] %}