CBQE-2404 update tap stats to dcp stats in 3.0.x

Change-Id: I28f652b59161788d1223614fb29b958bf78fa29a
Reviewed-on: http://review.couchbase.org/41180
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Thuan Nguyen <soccon@gmail.com>