pkg/cmd: fix ineffassign issues

pkg/cmd/grafana-server/main.go

@@ -100,9 +100,9 @@ func main() {
 }
 
 func listenToSystemSignals(server *GrafanaServerImpl, shutdownCompleted chan int) {
+	var code int
 	signalChan := make(chan os.Signal, 1)
 	ignoreChan := make(chan os.Signal, 1)
-	code := 0
 
 	signal.Notify(ignoreChan, syscall.SIGHUP)
 	signal.Notify(signalChan, os.Interrupt, os.Kill, syscall.SIGTERM)