Updated tests to use constants via the Harness.

This change is to allow the harness to easily swap out what
couchnode implementation is being used on the fly.

Change-Id: Ie01dcdac6955f966ac2368c0105fa0a3c977a784
Reviewed-on: http://review.couchbase.org/31001
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Brett Lawson <brett19@gmail.com>