[WIP] Redis configuration seems to break. Try some fix.

Somehow, `Redis` cookbook deploys the configuration file
for a newer `Redis` and the `Redis` installed on the sensu server
does not support the parameter written on it.

Modify the configration file as follows:

## before
```
notify-keyspace-events ""
```

### after
```
# notify-keyspace-events ""
```


see: https://github.com/brianbianco/redisio/pull/150