MB-11433: Don't aggregate upr/tap stats separately from the total

If we aggregate stats separately from the total then this can lead
to the sub-aggregate stats to not add up to the total.

Change-Id: If14a530fdc1627f6a01c797dff25ee74e9980d7b
Reviewed-on: http://review.couchbase.org/38923
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>