redis-cli prompt bug fix

after failing connect to server through redis-cli 

and try to redis server using "redis-server"

It couldn't update the redis-cli prompt 

before:
```c
charsyam@ubuntu:~/projects/redis-charsyam/src$ redis-cli -p 3000
Could not connect to Redis at 127.0.0.1:3000: Connection refused
not connected> connect 127.0.0.1 6379
redis 127.0.0.1:3000> <-- it isn't updated.
```

applying this patch.
```c
charsyam@ubuntu:~/projects/redis-charsyam/src$ ./redis-cli -p 3000
Could not connect to Redis at 127.0.0.1:3000: Connection refused
not connected> connect 127.0.0.1 6379
redis 127.0.0.1:6379>
```

It is updated well.