Fixing iostat format issue for ubuntu
Fixing iostat format issue for ubuntu

Change-Id: Icbd728a2e5c8976fc10dc870c09c5124d80a6b01
Reviewed-on: http://review.couchbase.org/c/perfrunner/+/137365
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Bo-Chun Wang <bb86fd206c9c35341feb9b50e74a74a83e254d63@couchbase.com>

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