Get returns detected category of network environment during detecting region id for determined axt server domain, otherwise NetworkCategoryUnknown.

Set wraps atomic store action for network category indicator.

In some cloud environment the metaserver(100.100.100.200) is provided, and axt server domain can be retrieved from http://100.100.100.200/latest/global-config/aliyun-assist-server-url , which is slightly different with traditional resolution process in VPC network.