update urfave/cli to 8ba6f23b6e36d03666a14bd9421f5e3efcb59aca

relate to https://github.com/containerd/containerd/pull/723

Signed-off-by: Lei Jitang <leijitang@huawei.com>

vendor/github.com/urfave/cli/help.go

@@ -64,7 +64,7 @@ OPTIONS:
 // cli.go uses text/template to render templates. You can
 // render custom help text by setting this variable.
 var SubcommandHelpTemplate = `NAME:
-   {{.HelpName}} - {{.Usage}}
+   {{.HelpName}} - {{if .Description}}{{.Description}}{{else}}{{.Usage}}{{end}}
 
 USAGE:
    {{.HelpName}} command{{if .VisibleFlags}} [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}