NCBC-503: CouchbaseCluster construction is missing un/pw

When attempting to use a bucket that requires authentication, the request
fails with 401 unauthorized. This patch fixes the issue by passing the
username and password when making the request for a bucket.

Change-Id: I3e192afae7c3cc4c03d2afd575aa0ca66af86382
Reviewed-on: http://review.couchbase.org/37869
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>