Fix scheduler and controller selectors for Kubespray

- refs:https://github.com/prometheus-operator/kube-prometheus/pull/916
- kubespray uses kubeadm, so it is good to inherit it

jsonnet/kube-prometheus/platforms/kubespray.libsonnet

-local service(name, namespace, labels, selector, ports) = {
-  apiVersion: 'v1',
-  kind: 'Service',
-  metadata: {
-    name: name,
-    namespace: namespace,
-    labels: labels,
-  },
-  spec: {
-    ports+: ports,
-    selector: selector,
-    clusterIP: 'None',
-  },
-};
-
-{
-
-  kubernetesControlPlane+: {
-    kubeControllerManagerPrometheusDiscoveryService: service(
-      'kube-controller-manager-prometheus-discovery',
-      'kube-system',
-      { 'app.kubernetes.io/name': 'kube-controller-manager' },
-      { 'app.kubernetes.io/name': 'kube-controller-manager' },
-      [{ name: 'https-metrics', port: 10257, targetPort: 10257 }]
-    ),
-
-    kubeSchedulerPrometheusDiscoveryService: service(
-      'kube-scheduler-prometheus-discovery',
-      'kube-system',
-      { 'app.kubernetes.io/name': 'kube-scheduler' },
-      { 'app.kubernetes.io/name': 'kube-scheduler' },
-      [{ name: 'https-metrics', port: 10259, targetPort: 10259 }],
-    ),
-
-    serviceMonitorKubeScheduler+: {
-      spec+: {
-        selector+: {
-          matchLabels: {
-            'app.kubernetes.io/name': 'kube-scheduler',
-          },
-        },
-      },
-    },
-
-    serviceMonitorKubeControllerManager+: {
-      spec+: {
-        selector+: {
-          matchLabels: {
-            'app.kubernetes.io/name': 'kube-controller-manager',
-          },
-        },
-      },
-    },
-
-  },
-}
+(import './kubeadm.libsonnet')