Fixed servers with FQDN not properly resolving.

If a bucket configuration returned from a Couchbase cluster contains a fully qualified domain name instead of an IP address, `CouchbaseConfigContext` will not properly resolve the endpoint, resulting in a null `KeyMapper`. Upon any operation that requires the `KeyMapper`, the Couchbase .Net client will throw a NullReferenceException.

Attached is a failing test and the proposed fix to `UriExtensions`.