Avoid multiple invocations of afterConnectionClosed

This change ensures the state of a SockJS session is set to CLOSED
immediately after close is invoked. This avoids duplicate invocations
of afterConnectionClosed in WebSocket transport.

Issue: SPR-11884

Author: rstoyanchev

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java

@@ -271,6 +271,7 @@ public final void close(CloseStatus status) throws IOException {
 			if (logger.isInfoEnabled()) {
 				logger.info("Closing SockJS session " + getId() + " with " + status);
 			}
+			this.state = State.CLOSED;
 			try {
 				if (isActive() && !CloseStatus.SESSION_NOT_RELIABLE.equals(status)) {
 					try {
@@ -285,7 +286,6 @@ public final void close(CloseStatus status) throws IOException {
 				disconnect(status);
 			}
 			finally {
-				this.state = State.CLOSED;
 				try {
 					this.handler.afterConnectionClosed(this, status);
 				}