[ReactNative] Explictly set displayName on tests

Summary:
@public

For some weird reason sometimes displayName is undefined on the OSS tests, manually
set it for now to unbreak the tests.

Test Plan: Run the tests on OSS

Examples/UIExplorer/UIExplorerIntegrationTests/js/AppEventsTest.js

@@ -53,6 +53,8 @@ var AppEventsTest = React.createClass({
   }
 });
 
+AppEventsTest.displayName = 'AppEventsTest';
+
 var styles = StyleSheet.create({
   container: {
     margin: 40,