Bug 1361818 - Make sure TPS is aware sync's collection.get method is asynchronous now r=markh

Ideally we'd convert this to promises, but this function is already full of
promiseSpinningly's and removing them all is too much work for this bug.

MozReview-Commit-ID: 144JFRwejTb

--HG--
extra : rebase_source : 40371c6cfeee9fddffe4b737cbb98fecb424b719

services/sync/tps/extensions/tps/resource/tps.jsm

@@ -624,7 +624,7 @@ var TPS = {
         item.decrypt(collectionKey);
         items.push(item.cleartext);
       };
-      collection.get();
+      Async.promiseSpinningly(collection.get());
       return items;
     };
     let serverRecordDumpStr;