plugins: fix usage for plugin commands

Signed-off-by: Tibor Vass <tibor@docker.com>
Upstream-commit: 65ed9daf70ccf0027f4eac8049667130deb249ed
Component: engine

components/engine/api/client/plugin/enable.go

@@ -11,7 +11,7 @@ import (
 
 func newEnableCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "enable",
+		Use:   "enable PLUGIN",
 		Short: "Enable a plugin",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {