Issue title: config command leaks
 Issue body: I use spring-session 1.2.1 with springboot 1.4.0.
I check client list using redis-cli, config command does not closed.

```
116.69.203.115:6379> client list
id=388 addr=116.69.203.115:37054 fd=5 name= age=682 idle=667 flags=N db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=0 oll=0 omem=0 events=r cmd=config
```

I guess EnableRedisKeyspaceNotificationsInitializer should be close after configure.

```
    static class EnableRedisKeyspaceNotificationsInitializer implements InitializingBean {
        private final RedisConnectionFactory connectionFactory;

        private ConfigureRedisAction configure;

        EnableRedisKeyspaceNotificationsInitializer(
                RedisConnectionFactory connectionFactory,
                ConfigureRedisAction configure) {
            this.connectionFactory = connectionFactory;
            this.configure = configure;
        }

        public void afterPropertiesSet() throws Exception {
            RedisConnection connection = this.connectionFactory.getConnection();
            this.configure.configure(connection);
        }
    }
```

 Comments: 
 Comment 0: Closed via 802e0e7
{'source': 'GithubIssues', 'repo_name_with_owner': 'spring-projects/spring-session', 'issue_id': 176542550, 'repo_stars': 1750.0}