Rename TAP-specific variables and functions to generic ones.

Change-Id: I02f4b3fa317e109c2ab6105a77a2379c3aa6ce83
Reviewed-on: http://review.couchbase.org/39252
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>