DEV: speed up ember acceptance tests

## Before

```
Acceptance: Composer::Image resizing buttons: 7985ms
Acceptance: Composer::Edit the first post: 3854ms
Acceptance: Composer::Composer with dirty edit can toggle to another edit: 3707ms
Acceptance: Composer::Composer can toggle between edit and reply: 3704ms
Acceptance: Composer::Tests the Composer controls: 3685ms
Acceptance: Composer::Composer draft with dirty reply can toggle to edit: 3670ms
Acceptance: Composer::Composer can toggle layouts (open, fullscreen and draft): 3278ms
Acceptance: Composer::Switching composer whisper state: 3266ms
Acceptance: Composer::Create a topic with server side errors: 3253ms
Acceptance: Composer::Composer with dirty reply can toggle to edit: 3189ms
Acceptance: Composer::Create a Topic: 3168ms
Acceptance: Composer::Create an enqueued Topic: 2767ms
Acceptance: Composer::Posting on a different topic: 2394ms
Acceptance: Composer::Composer can switch between edits: 2318ms
Acceptance: Composer::Create an enqueued Reply: 2317ms
Acceptance: Composer::Create a Reply: 2292ms
Acceptance: Composer::Checks for existing draft: 1696ms
Acceptance: Composer::Composer can toggle between reply and createTopic: 1415ms
Acceptance: Composer::Composer can toggle whispers: 1296ms
Acceptance: Composer::Loading draft also replaces the recipients: 594ms
```

## After

```
Acceptance: Composer::Composer can toggle layouts (open, fullscreen and draft): 2305ms
Acceptance: Composer::Switching composer whisper state: 2205ms
Acceptance: Composer::Composer draft with dirty reply can toggle to edit: 2185ms
Acceptance: Composer::Composer can toggle between edit and reply: 1719ms
Acceptance: Composer::Composer with dirty edit can toggle to another edit: 1682ms
Acceptance: Composer::Composer with dirty reply can toggle to edit: 1657ms
Acceptance: Composer::Composer can toggle between reply and createTopic: 1412ms
Acceptance: Composer::Posting on a different topic: 1341ms
Acceptance: Composer::Edit the first post: 1327ms
Acceptance: Composer::Create an enqueued Reply: 1306ms
Acceptance: Composer::Composer can toggle whispers: 1265ms
Acceptance: Composer::Composer can switch between edits: 1260ms
Acceptance: Composer::Create a Reply: 1259ms
Acceptance: Composer::Create a topic with server side errors: 1183ms
Acceptance: Composer::Checks for existing draft: 1172ms
Acceptance: Composer::Create a Topic: 1130ms
Acceptance: Composer::Image resizing buttons: 921ms
Acceptance: Composer::Create an enqueued Topic: 731ms
Acceptance: Composer::Tests the Composer controls: 654ms
Acceptance: Composer::Loading draft also replaces the recipients: 540ms

```


That is not a typo... image resizing button went from 8 seconds to 1 second

app/assets/javascripts/discourse/models/composer.js.es6

@@ -1032,7 +1032,7 @@ const Composer = RestModel.extend({
           self.set("draftConflictUser", null);
           self._clearingStatus = null;
         },
-        1000
+        Ember.Test ? 0 : 1000
       );
     }
   }.observes("title", "reply")