Fix lint errors.

cmd/step-ca/main.go

@@ -115,7 +115,7 @@ intermediate private key.`,
 	app.Writer = os.Stdout
 	app.ErrWriter = os.Stderr
 	app.Commands = []cli.Command{
-		cli.Command{
+		{
 			Name:  "version",
 			Usage: "Displays the current version of the cli",
 			// Command prints out the current version of the tool
@@ -124,7 +124,7 @@ intermediate private key.`,
 				return nil
 			},
 		},
-		cli.Command{
+		{
 			Name:      "help",
 			Aliases:   []string{"h"},
 			Usage:     "displays help for the specified command or command group",