CBQE-1310: add rebalance progress tests UI

Change-Id: I609c73757b7b524e8c9da00c5d80f7ee9a343a33
Reviewed-on: http://review.couchbase.org/27424
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>