fix: also set alertmanager_namespace in prometheus_config (#420)

Author: Duologic

prometheus-ksonnet/lib/prometheus-config.libsonnet

@@ -30,7 +30,7 @@
                 action: 'keep',
               }, {
                 source_labels: ['__meta_kubernetes_namespace'],
-                regex: $._config.namespace,
+                regex: $._config.alertmanager_namespace,
                 action: 'keep',
               }, {
                 // This prevents port-less containers and the gossip ports from showing up.
@@ -46,7 +46,7 @@
           api_version: 'v2',
           path_prefix: $._config.alertmanager_path,
           static_configs: [{ targets: [
-            'alertmanager-%d.alertmanager.%s.svc.%s.%s:%s' % [i, $._config.namespace, cluster, $._config.cluster_dns_tld, $._config.alertmanager_port]
+            'alertmanager-%d.alertmanager.%s.svc.%s.%s:%s' % [i, $._config.alertmanager_namespace, cluster, $._config.cluster_dns_tld, $._config.alertmanager_port]
             for cluster in std.objectFields($._config.alertmanager_clusters)
             if $._config.cluster_name != cluster && $._config.alertmanager_clusters[cluster].global && $._config.alertmanager_clusters[cluster].replicas > 1
             for i in std.range(0, $._config.alertmanager_clusters[cluster].replicas - 1)