MB-11551 detailed rebalance progress for upr vbuckets

Change-Id: Ic9f39f6d2ab43a008cf8f0d92674b3bae534b0cb
Reviewed-on: http://review.couchbase.org/38978
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>