CBD-909: add vperf DGM config for SSD cluster

Change-Id: Ia40f5b241a8c08ebb066c22bf70f5dc21b1ad9ba
Reviewed-on: http://review.couchbase.org/25344
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>
Tested-by: Pavel Paulau <pavel.paulau@gmail.com>