CBLT-170:  SGW_PKG is a tarball

Change-Id: I70272ffeef90f40a0b71ac904408b36850eff351
Reviewed-on: http://review.couchbase.org/35736
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>