CBLT-237: always create artifacts; only use UPLOAD_ARTIFACTS to determine whether to upload them

Change-Id: I35fb9bc35ea9d4245d92615b0e833fd395445f6d
Reviewed-on: http://review.couchbase.org/33983
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>