CBQE-2344: dml merge tests

Change-Id: I7f4c2a5372aed336de0d8d5bba559162464de1b0
Reviewed-on: http://review.couchbase.org/42165
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>