GH-3744: Fix ServerWebSocketContainer.stop()

Fixes #3744

The `ServerWebSocketContainer.stop()` accidentally calls `this.handshakeHandler.start()`

**Cherry-pick to `5.5.x`**

Author: Sorieee

spring-integration-websocket/src/main/java/org/springframework/integration/websocket/ServerWebSocketContainer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -232,7 +232,7 @@ public synchronized void start() {
 	@Override
 	public void stop() {
 		if (isRunning()) {
-			((Lifecycle) this.handshakeHandler).start();
+			((Lifecycle) this.handshakeHandler).stop();
 		}
 	}