CBD-792: Reduce run time to 2 hours

- xperf XDCR tests
- 5% writes

Change-Id: I01e08aa3b2b82377146c76aef3a5b5ac9daf19fb
Reviewed-on: http://review.couchbase.org/24559
Reviewed-by: abhinav dangeti <abhinav.dangeti@gmail.com>
Tested-by: abhinav dangeti <abhinav.dangeti@gmail.com>