Redis save uses then

We need to ensure that the session id is changed before we save the
changes. Otherwise the rename of the session id will override the
changes we just made.

Fixes: gh-1428

spring-session-data-redis/src/main/java/org/springframework/session/data/redis/ReactiveRedisOperationsSessionRepository.java

@@ -143,7 +143,8 @@ public class ReactiveRedisOperationsSessionRepository implements
 
 	@Override
 	public Mono<Void> save(RedisSession session) {
-		Mono<Void> result = session.saveChangeSessionId().and(session.saveDelta())
+		Mono<Void> result = session.saveChangeSessionId()
+				.then(session.saveDelta())
 				.and((s) -> {
 					session.isNew = false;
 					s.onComplete();