CBQE-1354: add test with 100 concurrent queries

Change-Id: I609f09054e95ec34d17a2734be8173fb7198992a
Reviewed-on: http://review.couchbase.org/27338
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>