[BUGFIX release] restore internalModels GUID_KEY’s

(cherry picked from commit 4dcb83d)

Author: stefanpenner

addon/-private/system/model/internal-model.js

@@ -120,7 +120,10 @@ export default class InternalModel {
   constructor(modelName, id, store, data) {
     heimdall.increment(new_InternalModel);
     this.id = id;
-    this._internalId = InternalModelReferenceId++;
+
+    // this ensure ordered set can quickly identify this as unique
+    this[Ember.GUID_KEY] = InternalModelReferenceId++ + 'internal-model';
+
     this.store = store;
     this.modelName = modelName;
     this._loadingPromise = null;