添加配置项，可以为内存文件存储添加远程服务地址

broker/src/main/java/io/moquette/server/Server.java

@@ -346,6 +346,7 @@ public class Server {
             file.mkdirs();
         }
         ServerSetting.setRoot(file);
+        MediaServerConfig.FILE_STROAGE_REMOTE_SERVER_URL = config.getProperty(FILE_STORAGE_REMOTE_SERVER_URL);
 
         MediaServerConfig.USER_QINIU = Integer.parseInt(config.getProperty(BrokerConstants.USER_QINIU)) > 0;
     }

broker/src/main/java/io/moquette/server/config/MediaServerConfig.java

@@ -27,6 +27,7 @@ public class MediaServerConfig {
     public static String SERVER_IP = "localhost";
     public static int HTTP_SERVER_PORT = 8080;
     public static String FILE_STROAGE_ROOT = "fs";
+    public static String FILE_STROAGE_REMOTE_SERVER_URL;
     public static boolean USER_QINIU = false;