support legacy session data.

fixes https://github.com/c9/newclient/issues/6955

should be reverted when all current session are expired (one week after this is released)

plugins/c9.preview/preview.handler.js

@@ -136,7 +136,7 @@ define(function(require, exports, module) {
                 var path = req.params.path;
                 var url = req.proxyUrl + path;
                 if (req.session.token)
-                    url += "?access_token=" + encodeURIComponent(req.session.token);
+                    url += "?access_token=" + encodeURIComponent(req.session.token.id || req.session.token);
 
                 var parsedUrl = parseUrl(url);
                 var httpModule = parsedUrl.protocol == "https:" ? https : http;