Initialise Container cdn data to defaults if no cdn_connection.

AFAICT, currently the Container.cdn_enabled property [errors when your client doesn't have a cdn connection](http://paste.ubuntu.com/6478049/) (ie. using non-rackspace openstack).

This branch ensures that when a Container object is initialised with a client, it sets the default cdn details if the client doesn't have a cdn connection, otherwise the previous behaviour of setting the values to be loaded lazily.

Notes
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I initially thought the Client.cdn_enabled class property was relevant, but then found it's never actually referenced anywhere, and the tests pass without it. So either there's code out there depending on a class property that always returns False, or it's not used at all. I'm assuming it should be removed, but didn't make that call given that it's a public property.

I added some whitespace to the 2 relevant tests only because it wasn't obvious (to me) where the test-setup, code execution and expectations started/ended. If that's not OK, happy to remove it.