Corrects record update API for CloudDNSManager and CloudDNSDomain

Continuation of #455 .
* Update failing unitest
* Made against working branch

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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.

While the unit tests passed, this line 881 seems too long for the pep8 check so it killed the build. Could you break the line before `body=...` and put that on its own line so it lines up vertically with `error_class=...`? That should make it pass.