MB-100 Fix conf file for flush tests

Change-Id: I0cff66576fa2c4d124a8fe46ec119678fb135ff8
Reviewed-on: http://review.couchbase.org/24295
Reviewed-by: Deepkaran Salooja <deepkaran.salooja@globallogic.com>
Tested-by: Deepkaran Salooja <deepkaran.salooja@globallogic.com>