MB-100: added high thruput testcase

Change-Id: Iddf8b90e5db6d447954748de44036c00fc8e3c75
Reviewed-on: http://review.couchbase.org/28031
Reviewed-by: Ronnie Sun <ronnie@couchbase.com>
Tested-by: Ronnie Sun <ronnie@couchbase.com>