Add extensible command line flags to Alertmanager

Alertmanager is configured similarly to Prometheus. This change
brings the utils.command_line_flags template from the osh-infra
prometheus chart to Alertmanager, allowing these flags to be
configured in Values.yaml

Change-Id: Ieca94c09881bc52b62500efa4c6f8730b9208d3b

prometheus-alertmanager/Chart.yaml

@@ -15,7 +15,7 @@ apiVersion: v1
 appVersion: v0.20.0
 description: OpenStack-Helm Alertmanager for Prometheus
 name: prometheus-alertmanager
-version: 0.1.1
+version: 0.1.2
 home: https://prometheus.io/docs/alerting/alertmanager/
 sources:
   - https://github.com/prometheus/alertmanager

prometheus-alertmanager/templates/bin/_alertmanager.sh.tpl

@@ -20,8 +20,10 @@ COMMAND="${@:-start}"
 function start () {
   exec /bin/alertmanager \
     --config.file=/etc/alertmanager/config.yml \
-    --storage.path={{ .Values.conf.command_flags.alertmanager.storage.path }} \
-    --cluster.listen-address={{ .Values.conf.command_flags.alertmanager.cluster.listen_address }} \
+{{- range $flag, $value := .Values.conf.command_flags.alertmanager }}
+{{- $flag := $flag | replace "_" "-" }}
+{{ printf "--%s=%s" $flag $value | indent 4 }} \
+{{- end }}
     $(generate_peers)
 }
 

prometheus-alertmanager/values.yaml

@@ -250,10 +250,8 @@ network_policy:
 conf:
   command_flags:
     alertmanager:
-      storage:
-        path: /var/lib/alertmanager/data
-      cluster:
-        listen_address: "0.0.0.0:9094"
+      storage.path: /var/lib/alertmanager/data
+      cluster.listen_address: "0.0.0.0:9094"
     snmpnotifier:
       alert_default_severity: crititcal
       alert_severities: "critical,warning,info,page"