simplify error handling from get_remote_bucket_by_ref

Change-Id: I602c18c45564a8b38c5a3c4e0b7b9bd72a8eeb0d
Reviewed-on: http://review.couchbase.org/38448
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>