Corrects API for CloudDNSManager's update_records and CloudDNSDomain upd...

CloudDNSDomain.update_record calls to CloudDNSManager.update_records.  update_records did not produce the correct JSON format.  

See the example request at http://docs.rackspace.com/cdns/api/v1.0/cdns-devguide/content/PUT_updateRecords_v1.0__account__domains__domainId__records_records.html

This patch corrects that and ensures that that records paramater passed to CloudDNSManager.update_records is a list.