metropolis/cli/metroctl: don't print usage for runtime errors

Change-Id: I91fdca45e874ea1ec9112df556a9a7392fd45bfd
Fixes: https://github.com/monogon-dev/monogon/issues/352
Reviewed-on: https://review.monogon.dev/c/monogon/+/3440
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/cli/metroctl/cmd_certs.go b/metropolis/cli/metroctl/cmd_certs.go
index d914c83..8475546 100644
--- a/metropolis/cli/metroctl/cmd_certs.go
+++ b/metropolis/cli/metroctl/cmd_certs.go
@@ -48,5 +48,5 @@
 		}
 		log.Println("Wrote files to current dir: cert.pem, key.pem")
 	},
-	Args: cobra.NoArgs,
+	Args: PrintUsageOnWrongArgs(cobra.NoArgs),
 }