[Tree] Refresh properly on mutation

...by removing the incorrect expectation that a domain object
(and not just its model) will be passed in when mutation occurs.
Addresses #745.

platform/commonUI/general/test/ui/TreeViewSpec.js

@@ -161,7 +161,7 @@ define([
                 beforeEach(function () {
                     mockComposition.pop();
                     testCapabilities.mutation.listen
-                        .mostRecentCall.args[0](mockDomainObject);
+                        .mostRecentCall.args[0](mockDomainObject.getModel());
                     waitForCompositionCallback();
                 });