Redefine Infusionsoft_ProductService::ping

[eversionsystems]

PHP warning about incorrect definition. Change definition of function to the following in ProductService.php

class Infusionsoft_ProductService extends Infusionsoft_ProductServiceBase
{
    public static function ping($serviceName, Infusionsoft_App $app = null)
    {
        return parent::ping('ProductService', $app);
    }