CBQE-1809: fix negative upgrade tests

Change-Id: Id39bb5b7672ff795b70cf435512cdd35a214470b
Reviewed-on: http://review.couchbase.org/31477
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>