fix js error that happens if /node/controller/rename returns

...ERR_CONNECTION_REFUSED

Change-Id: I0fe1e0f0ff7cf01a1d553bc3e4964f69767d53d3
Reviewed-on: http://review.couchbase.org/36160
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>