refactor help func in CLI

Signed-off-by: Victor Vieux <victorvieux@gmail.com>
Upstream-commit: 55908f8a82
Component: cli

components/cli/command/plugin/cmd.go

@@ -12,10 +12,7 @@ func NewPluginCommand(dockerCli *command.DockerCli) *cobra.Command {
 		Use:   "plugin",
 		Short: "Manage plugins",
 		Args:  cli.NoArgs,
-		Run: func(cmd *cobra.Command, args []string) {
-			cmd.SetOutput(dockerCli.Err())
-			cmd.HelpFunc()(cmd, args)
-		},
+		RunE:  dockerCli.ShowHelp,
 	}
 
 	cmd.AddCommand(