Fix the syntax for the curator delete cron.

For the Logstash 1.4 branch: this corrects the syntax for the elasticsearch curator cron job in the curator provider. 

Before:
```
[logstash]$ crontab -l
# Chef Name: curator-server
0 * * * * curator --host testing-es-logstashbalancer -d 1 &> /dev/null
[logstash]$ curator --host testing-es-logstashbalancer -d 1
usage: curator [-h] [-v] [--host HOST] [--url_prefix URL_PREFIX] [--port PORT]
               [--ssl] [--auth AUTH] [-t TIMEOUT] [--master-only] [-n] [-D]
               [--loglevel LOG_LEVEL] [-l LOG_FILE]
               {show,allocation,alias,snapshot,close,bloom,optimize,delete}
               ...
curator: error: argument command: invalid choice: '1' (choose from 'show', 'allocation', 'alias', 'snapshot', 'close', 'bloom', 'optimize', 'delete')
```
After fix:
```
[logstash]$ crontab -l
# Chef Name: curator-server
0 * * * * curator --host testing-es-logstashbalancer delete --older-than 1 &> /dev/null
[logstash]$ curator --host testing-es-logstashbalancer delete --older-than 1
<snip>
2014-07-23T14:12:08.717 INFO                        main:674  Done in 0:00:00.058335.
```

Tested with curator version 1.1.3.