Fully qualify the Singleton so the stripped import doesn't cause issu…

…es in the opensource build.

extensions/struts2/test/com/google/inject/struts2/Struts2FactoryTest.java

@@ -52,7 +52,8 @@ protected Injector getInjector() {
             @Override
             protected void configureServlets() {
               // Struts 2 setup
-              bind(StrutsPrepareAndExecuteFilter.class).in(Singleton.class);
+              bind(StrutsPrepareAndExecuteFilter.class)
+                  .in(com.google.inject.Singleton.class);
               filter("/*").through(StrutsPrepareAndExecuteFilter.class);
             }
           },