CBQE-640: add sample bucket UI test

Change-Id: I94114f5974e14240c657cc8d280c35a3d5d10d42
Reviewed-on: http://review.couchbase.org/29248
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>