MB-8578: Add stats uuid

Change-Id: I6c19fc48f98e9dbe5bd19495d8d0f122cb06914b
Reviewed-on: http://review.couchbase.org/27354
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>