MB-100: fix load_with_async_ops_and_joint_sets

for case doc-ops=create-update,doc-ops-dest=create-update

Change-Id: Ie7b318322f76c54a0aab3c518dbd1069161eb6b1
Reviewed-on: http://review.couchbase.org/24855
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>