GH-1193: Fix Late Binding

LateBinding fields must be volatile for the test to be sure
to get the value (they should be volatile anyway).

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binding/BindingService.java

@@ -330,9 +330,9 @@ public class BindingService {
 
 	private static class LateBinding<T> implements Binding<T> {
 
-		private Binding<T> delegate;
+		private volatile Binding<T> delegate;
 
-		private boolean unbound;
+		private volatile boolean unbound;
 
 		LateBinding() {
 			super();