NCBC-713: Ensure that multiple buckets can be added to a configuration

Change-Id: I9cdad08dbb078f13fcf948c1992d78ee80230514
Reviewed-on: http://review.couchbase.org/42858
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>