Cluster.bucket needs kwargs for the tests to work against the mock

And the tests need to add the connargs (see ClusterTestCase.setUp). But only for the mock - when running against a real server we don't need it. I didn't want to fix this as part of other fixes, so making a new issue for it. However this seems really bad and worth reworking the test underpinnings to not need it. It really makes one wonder exactly what we are testing