Fixed standalone config, small refactor (#589)

cli/cmd/install.go

@@ -1,7 +1,9 @@
 package cmd
 
 import (
+	"fmt"
 	"github.com/spf13/cobra"
+	"github.com/up9inc/mizu/cli/config"
 	"github.com/up9inc/mizu/cli/telemetry"
 )
 
@@ -13,6 +15,13 @@ var installCmd = &cobra.Command{
 		runMizuInstall()
 		return nil
 	},
+	PreRunE: func(cmd *cobra.Command, args []string) error {
+		if config.Config.IsNsRestrictedMode() {
+			return fmt.Errorf("install is not supported in restricted namespace mode")
+		}
+
+		return nil
+	},
 }
 
 func init() {