Refactor: use the validator/executor for tap as well

Change-Id: Ia99ac37494018f856fc9596b6ff6efd72ea8f4f3
Reviewed-on: http://review.couchbase.org/28942
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>