Fix display name for ios voice messages

iOS populates a filename for voice messages which was overruling our check for
the voice message flag when choosing the display name.

// FREEBIE

js/views/attachment_view.js

@@ -127,12 +127,12 @@
         }
     },
     displayName: function() {
-        if (this.model.fileName) {
-            return this.model.fileName;
-        }
         if (this.isVoiceMessage()) {
             return i18n('voiceMessage');
         }
+        if (this.model.fileName) {
+            return this.model.fileName;
+        }
         if (this.isAudio() || this.isVideo()) {
             return i18n('mediaMssage');
         }