Ensure LMS passes correct group_id when querying content

TNL-23
One way to do this that would be much less brittle would be to check the request URL instead of looking for a specific index in the list of calls. You could define `cs_endpoint` instead of `cs_call_num` and then do something like `mock_request.call_args.filter(lambda args: args[1].endswith(self.cs_endpoint))[0]`