CBQE-0: fix tuq sum/avg tests

Change-Id: I09d90a6ce18e389af6f277221aa4f5e42687ebda
Reviewed-on: http://review.couchbase.org/30868
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>