From my experience, this plugin does not currently support Azure China. I've coded an application of my own that targets Azure storage - the same API can be used for both Global Azure and China Azure. However, there is one value you need to change.
Example working with Blobs from the Azure Python SDK, should be quite similar for Table Storage:
The old Windows-only add-on referenced in original question has been pulled down. Take a look at the new cross-platform Splunk Add-on for Microsoft Azure which pulls data from Azure Storage API using Azure Storage Python SDK.
Among others, the Add-on leverages TableService and BlockBlobService which use core.windows.net endpoint for Azure cloud. You'll need to set endpoint_suffix to core.chinacloudapi.cn endpoint to access Azure China cloud instead.