skip get_disk_stats if the cluster is using software raid
skip get_disk_stats if the cluster is using software raid

Change-Id: I6f2b2966720f00756ac1648db356b1986db38664
Reviewed-on: http://review.couchbase.org/121525
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Korrigan Clark <11cf3ebdc6cba78053c91b2fd94cb21b47d0d02e@couchbase.com>

couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner,couchbase/perfrunner