CBQE-2304 add method to start, get status and cancel cluster-wide collectinfo

Change-Id: I0e3da03005f5630c796be7de41d45b6508132478
Reviewed-on: http://review.couchbase.org/39066
Tested-by: Thuan Nguyen <soccon@gmail.com>
Reviewed-by: Thuan Nguyen <soccon@gmail.com>