CBQE-2429: DML merge tests

Change-Id: Iecf924eb257a88e22aff08cd25d06e7b59127e6b
Reviewed-on: http://review.couchbase.org/42279
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>