Fix smoke test F0637FuzzySearch.rb.
Fix smoke test F0637FuzzySearch.rb.

In order to make smoke test F0637FuzzySearch.rb pass, when the request parameter
"query_prune" is false, make the "rank_boundary" to zero, so that no search results
would be pruned.

izenecloud/sf1r-lite,izenecloud/sf1r-lite,pombredanne/sf1r-lite,izenecloud/sf1r-lite,pombredanne/sf1r-lite,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-lite,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-ad-delivery,izenecloud/sf1r-ad-delivery,pombredanne/sf1r-lite,izenecloud/sf1r-lite,izenecloud/sf1r-ad-delivery,pombredanne/sf1r-lite,pombredanne/sf1r-lite