Connect to cluster with invalid connection string throws wrong error

Suggested release note:

`Cluster.connect()` now rejects connection strings that have no addresses (like "couchbase://"). Before this change, it would accept the invalid connection string, and subsequent operations would fail with a misleading error message: "The cluster does not support cluster-level queries"

Trying to connect to Couchbase using the latest version of the SDK throws the wrong error. I'm using completely invalid credentials, yet the SDK instead of showing some error saying that it could not connect, shows instead "The cluster does not support cluster-level queries (only Couchbase Server 6.5 and later) and no bucket is open. If an older Couchbase Server version is used, at least one bucket needs to be opened to dispatch this mgmt request!"