CBLT-159:  get packages from S3 not CBFS

Change-Id: I894cbe1cfe8b0eafd0d32a807327fe710ac64149
Reviewed-on: http://review.couchbase.org/37914
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>