Fix race condition in the SftpSessionFactoryTests

Related to: apache/mina-sshd#700

Author: artembilan

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/session/SftpSessionFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2024 the original author or authors.
+ * Copyright 2014-2025 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.
@@ -262,7 +262,8 @@ void clientSessionIsClosedOnSessionClose() throws Exception {
 			session.close();
 
 			assertThat(session.isOpen()).isFalse();
-			assertThat(clientSession.isClosed()).isTrue();
+			// TODO until https://github.com/apache/mina-sshd/issues/700
+			await().untilAsserted(() -> assertThat(clientSession.isClosed()).isTrue());
 
 			sftpSessionFactory.destroy();
 		}