record whether a pack is temporary in the pack itself

using the expiresAt field no longer determines if the pack is
temporary because archived packs have an expiresAt field added when
they are retrieved from s3

services/track-changes/app/coffee/PackManager.coffee

@@ -92,6 +92,7 @@ module.exports = PackManager =
 				end_ts: last.meta.end_ts
 			v: first.v
 			v_end: last.v
+			temporary: temporary
 		if temporary
 			newPack.expiresAt = new Date(Date.now() + 7 * DAYS)
 		logger.log {project_id, doc_id, newUpdates}, "inserting updates into new pack"