Embed NoopNetworkPlugin into other network plugins

Let Noop handle common functions.

pkg/kubelet/network/exec/exec.go

@@ -72,6 +72,8 @@ import (
 )
 
 type execNetworkPlugin struct {
+	network.NoopNetworkPlugin
+
 	execName string
 	execPath string
 	host     network.Host
@@ -120,9 +122,6 @@ func (plugin *execNetworkPlugin) getExecutable() string {
 	return path.Join(plugin.execPath, execName)
 }
 
-func (plugin *execNetworkPlugin) Event(name string, details map[string]interface{}) {
-}
-
 func (plugin *execNetworkPlugin) Name() string {
 	return plugin.execName
 }