检测configMap，重载Pod内的业务容器

Usage：

使用sidecar模式，跟业务进程运行在同一个Pod内，检测到configMap更新后，会自动触发Hook

       - name: prometheus-server-configmap-reload
          image: 'jimmidyson/configmap-reload:v0.3.0'
          args:
            - '--volume-dir=/etc/config'
            - '--webhook-url=http://127.0.0.1:9090/-/reload'       # 以prometheus为例，调用prom的reload api
          resources: {}
          volumeMounts:
            - name: config-volume
              readOnly: true
              mountPath: /etc/config

Parma：

开源地址

Usage of ./out/configmap-reload:
  -volume-dir value
        the config map volume directory to watch for updates; may be used multiple times
  -web.listen-address string
    	  address to listen on for web interface and telemetry. (default ":9533")
  -web.telemetry-path string
    	  path under which to expose metrics. (default "/metrics")
  -webhook-method string
        the HTTP method url to use to send the webhook (default "POST")
  -webhook-status-code int
        the HTTP status code indicating successful triggering of reload (default 200)
  -webhook-url string
        the url to send a request to when the specified config map volume directory has been updated
  -webhook-retries integer
        the amount of times to retry the webhook reload request