CBQE-0: minor fix in settings verification for upgrade tests

Change-Id: I73d964f4a55653ba26d25a19f5d3b50f0ee25fbd
Reviewed-on: http://review.couchbase.org/26407
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>