CCF.CChInvH: physicalClose() on ShutdownSignalException

The `publisherCallbackChannel.waitForConfirms()` may fail with a `ShutdownSignalException`
indicating that channel is closed on the broker.
So, treat it as a `TimeoutException` and proceed with a `physicalClose()` logic

**Auto-cherry-pick to `3.0.x`**

Related to spring-projects#2640

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/CachingConnectionFactory.java

@@ -1324,7 +1324,7 @@ private void returnToCache(ChannelProxy proxy) {
 								catch (InterruptedException ex) {
 									Thread.currentThread().interrupt();
 								}
-								catch (TimeoutException ex) {
+								catch (ShutdownSignalException | TimeoutException ex) {
 									// The channel didn't handle confirms, so close it altogether to avoid
 									// memory leaks for pending confirms
 									try {