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_k8scredplugin.go b/metropolis/cli/metroctl/cmd_k8scredplugin.go
index 0d1f318..8d84a9e 100644
--- a/metropolis/cli/metroctl/cmd_k8scredplugin.go
+++ b/metropolis/cli/metroctl/cmd_k8scredplugin.go
@@ -21,7 +21,7 @@
 	Long: `This implements a Kubernetes client-go credential plugin to
 authenticate client-go based callers including kubectl against a Metropolis
 cluster. This should never be directly called by end users.`,
-	Args:   cobra.ExactArgs(0),
+	Args:   PrintUsageOnWrongArgs(cobra.ExactArgs(0)),
 	Hidden: true,
 	Run:    doK8sCredPlugin,
 }