overview dashboard: Look up services by 'service' label, not job

Job can't be repeated across scrape jobs, service can

monitoring/dashboards/overview.jsonnet

@@ -32,7 +32,7 @@ local service_status_table = {
   type: "table",
   targets: [
     {
-      expr: 'sum(up{job="%s", role=~"%s"}) by (instance)' % [services[i], roles_for_service[services[i]]],
+      expr: 'sum(up{service="%s", role=~"%s"}) by (instance)' % [services[i], roles_for_service[services[i]]],
       intervalFactor: 1,
       format: "table",
       refId: refId(i),

monitoring/prometheus.jsonnet

@@ -42,6 +42,7 @@ local services = [
             labels: {
               instance: host,
               role: hosts[host][1],
+              service: service,
             },
           } for host in std.objectFields(hosts)
         ],