Expire timer updates: don't send if updated via remote message (#2473)

A recent change removed the type property to make markRead() behave
properly, but that broke our check 'should we send an update?' logic. So
instead of using `isIncoming()` we now use the thing we previously used
to determine whether a message was incoming: `receivedAt`.

js/models/conversations.js

@@ -925,11 +925,11 @@
         wrapDeferred(message.save()),
         wrapDeferred(this.save({ expireTimer })),
       ]).then(() => {
-        if (message.isIncoming()) {
+        // if change was made remotely, don't send it to the number/group
+        if (receivedAt) {
           return message;
         }
 
-        // change was made locally, send it to the number/group
         let sendFunc;
         if (this.get('type') === 'private') {
           sendFunc = textsecure.messaging.sendExpirationTimerUpdateToNumber;