SEC-2941: Default RequestPostProcessor overrides

Previously a default RequestPostProcessor overrode additional
RequestPostProcessor instances added to the request. This was due to
SPR-12945. Now that SPR-12945 is fixed, this commit adds a test to
ensure this stays fixed.

test/src/test/java/org/springframework/security/test/web/servlet/request/Sec2935Tests.java

@@ -103,7 +103,7 @@ public class Sec2935Tests {
 			.andExpect(authenticated().withUsername("user"));
 	}
 
-	@Ignore
+	// SEC-2941
 	@Test
 	public void defaultRequest() throws Exception {
 		mvc = MockMvcBuilders.webAppContextSetup(context)