add a new 1B rebalance-swap test with "Disk I/O optimized"
add a new 1B rebalance-swap test with "Disk I/O optimized"

Change-Id: I29b3f412c77722ba78488e94455bd06a032ac4c0
Reviewed-on: http://review.couchbase.org/c/perfrunner/+/126970
Reviewed-by: Bo-Chun Wang <bb86fd206c9c35341feb9b50e74a74a83e254d63@couchbase.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

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