config: add load/save config file

cmd/kvm/main.go

@@ -12,8 +12,16 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
+const ConfigFile = "/etc/rkkvm/rkkvm.yml"
+
 func main() {
-	config.Init()
+	if err := config.Load(ConfigFile); err != nil {
+		config.Init()
+		if err = config.Save(ConfigFile); err != nil {
+			log.Error(err)
+		}
+	}
+
 	cfg := config.Get()
 	lvl, err := log.ParseLevel(cfg.LogLevel)
 	if err == nil {