Add support for stats uuid

Change-Id: I3773916af7baf59b73cea07dfb50ef2aa68231f1
Reviewed-on: http://review.couchbase.org/27708
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>