exit status is always 0, even on error

The daemon should exit non-zero if there is an error (like when parsing the config file):

```
$ influxdb -pidfile /var/run/influxdb/influxdb.pid -config /etc/influxdb.conf
Couldn't parse configuration file: /etc/influxdb.conf
Near line 2, key '': Near line 19: Table names cannot contain '[' or ']'.
$ echo $?
0
```

<!---
@huboard:{"order":749.0,"milestone_order":1008,"custom_state":""}
-->