made bucketsListCell.refresh work even if nothing has changed

Which is important for hooks.js which always returns same stuff.

I.e. previously because we subscribed on bucketsListCell which uses
_.isEqual for equality we ended up not calling callback in hooks.js.

Now we subscribeOne on rawDetailedBuckets which has object identity
equality which causes refresh callback to work.

Change-Id: Ia5077e156426645368c760df2ad131914e37b8d3
Reviewed-on: http://review.couchbase.org/41008
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Pavel Blagodov <stochmail@gmail.com>
Tested-by: Pavel Blagodov <stochmail@gmail.com>