roles/icinga2: add dns monitoring for web services

roles/icinga2/files/icinga2/services.conf

@@ -143,3 +143,14 @@ apply Service "ldap_sync" {
   assign where host.vars.ldap_master
 }
 
+apply Service "dns" {
+  import "generic-service"
+
+  check_command = "dns"
+
+  if (host.vars.dns_a_record) {
+     vars.dns_expected_answer = host.vars.dns_a_record
+  }
+
+  assign where host.vars.host_type == "web service"
+}