CBLT-298:  renamed: rename_ios_artifacts.sh -> prepare_release_ios.sh

Change-Id: If57b5419511940a1b9ce937cfb34dd1815f495d0
Reviewed-on: http://review.couchbase.org/37871
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>