CBQE-0:tuq: fix array_prepend test

Change-Id: I091397cb56273e1eb7debc2d18ee19f71077a3e1
Reviewed-on: http://review.couchbase.org/31723
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>