CBQE-1531: create buckets and load items only in suite setup

Change-Id: I03635702da56922a6f625e517821d070fe345138
Reviewed-on: http://review.couchbase.org/29273
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>