Tweak RETRY_BACKOFF_RATELIMIT to take browser-request's CORS failures into account.

lib/scheduler.js

@@ -133,6 +133,12 @@ MatrixScheduler.RETRY_BACKOFF_RATELIMIT = function(event, attempts, err) {
         // client error; no amount of retrying with save you now.
         return -1;
     }
+    // we ship with browser-request which returns { cors: rejected } when trying
+    // with no connection, so if we match that, give up since they have no conn.
+    if (err.cors === "rejected") {
+        return -1;
+    }
+
     if (err.name === "M_LIMIT_EXCEEDED") {
         var waitTime = err.data.retry_after_ms;
         if (waitTime) {