modify kube-prometheus-static-etcd.libsonnet servicemonitorEtcd namespace (#592)

* Change the servicemonitorEtcd namespace kube-system to $._config.namespace

* delete  Watchdog of alert rule

* Revert "delete  Watchdog of alert rule"

This reverts commit 815b922ead.

Co-authored-by: tyger <tyger.cheng@oriente.com>

jsonnet/kube-prometheus/kube-prometheus-static-etcd.libsonnet

@@ -50,7 +50,7 @@ local k = import 'ksonnet/ksonnet.beta.4/k.libsonnet';
         kind: 'ServiceMonitor',
         metadata: {
           name: 'etcd',
-          namespace: 'kube-system',
+          namespace: $._config.namespace,
           labels: {
             'k8s-app': 'etcd',
           },