cmd/*: fail on unrecognized flags/arguments for component CLI

In case a malformed flag is passed to k8s components
such as "–foo", where "–" is not an ASCII dash character,
the components currently silently ignore the flag
and treat it as a positional argument.

Make k8s components/commands exit with an error if a positional argument
that is not empty is found. Include a custom error message for all
components except kubeadm, as cobra.NoArgs is used in a lot of
places already (can be fixed in a followup).

The kubelet already handles this properly - e.g.:
'unknown command: "–foo"'

This change affects:
- cloud-controller-manager
- kube-apiserver
- kube-controller-manager
- kube-proxy
- kubeadm {alpha|config|token|version}
- kubemark

Signed-off-by: Monis Khan <mok@vmware.com>
Signed-off-by: Lubomir I. Ivanov <lubomirivanov@vmware.com>

cmd/kube-proxy/app/server.go

@@ -294,10 +294,7 @@ func (o *Options) processHostnameOverrideFlag() error {
 }
 
 // Validate validates all the required options.
-func (o *Options) Validate(args []string) error {
-	if len(args) != 0 {
-		return errors.New("no arguments are supported")
-	}
+func (o *Options) Validate() error {
 	if errs := validation.Validate(o.config); len(errs) != 0 {
 		return errs.ToAggregate()
 	}
@@ -490,7 +487,7 @@ with the apiserver API to configure the proxy.`,
 			if err := opts.Complete(); err != nil {
 				klog.Fatalf("failed complete: %v", err)
 			}
-			if err := opts.Validate(args); err != nil {
+			if err := opts.Validate(); err != nil {
 				klog.Fatalf("failed validate: %v", err)
 			}
 
@@ -498,6 +495,14 @@ with the apiserver API to configure the proxy.`,
 				klog.Exit(err)
 			}
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 
 	var err error