内网环境的KML文件，无法通过ArcGIS JavaScript API加载KMLayer

【解决办法】：
kmlayer 默认使用了一个公网的ArcGIS Online kmservice 来处理kml文件，即kml文件需要先上传到公网，如果使用了内网地址，程序是无法正常工作的，参考API文档，如果本机上安装了Portal for ArcGIS的话，可以把kmservice设置为本地portal地址来绕过这个问题：
Note: The KMLLayer uses a utility service from ArcGIS.com, therefore your kml/kmz must be publicly accessible on the internet. If your kml/kmz files are behind the firewall you will need to set the esriConfig.defaults.kmlService to your own utility service. (Requires Portal for ArcGIS).

 require([esri/config],function(esriConfig){   esriConfig.defaults.kmlService =http://www.example.com/arcgis/sharing/kml;});