cmd/install: don't show usage on install failure

Before this patch, when the install fail (e.g. some validation failed)
the usage would be displayed. For example, when the minikube minium
version was not met:

     % go run ./cmd/cilium install
    🔮 Auto-detected Kubernetes kind: minikube
    ✨ Running "minikube" validation checks
    ❌ Validation test minimum-version failed: minimum version is ">=2.5.2", found version "1.16.0"
    ℹ️  You can disable the test with --disable-check=minimum-version
    Error: validation check for kind "minikube" failed: minimum version is ">=2.5.2", found version "1.16.0"
    Usage:
      cilium install [flags]

    Flags:
          --cluster-name string     Name of the cluster
          --datapath-mode string    Cilium version to install
          --disable-check strings   Disable a particular validation check
      -h, --help                    help for install
          --namespace string        Namespace to install Cilium into (default "kube-system")
          --version string          Cilium version to install

This patch make it so an install step error would not make cobra show
the usage.

See also spf13/cobra#340

Signed-off-by: Alexandre Perrin <alex@kaworu.ch>

internal/cli/cmd/install.go

@@ -32,6 +32,7 @@ func newCmdInstall() *cobra.Command {
 		Long:  ``,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			installer := install.NewK8sInstaller(k8sClient, params)
+			cmd.SilenceUsage = true
 			return installer.Install(context.Background())
 		},
 	}