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_install_usb.go b/metropolis/cli/metroctl/cmd_install_usb.go
index a9873b6..fcbcfa2 100644
--- a/metropolis/cli/metroctl/cmd_install_usb.go
+++ b/metropolis/cli/metroctl/cmd_install_usb.go
@@ -13,7 +13,7 @@
 	Use:     "genusb target",
 	Short:   "Generates a Metropolis installer disk or image.",
 	Example: "metroctl install --bundle=metropolis-v0.1.zip genusb /dev/sdx",
-	Args:    cobra.ExactArgs(1), // One positional argument: the target
+	Args:    PrintUsageOnWrongArgs(cobra.ExactArgs(1)), // One positional argument: the target
 	Run:     doGenUSB,
 }