Fix mysql collector

The MySQL collector will send duplicate metrics when using the publish option e.g.

publish = Com_delete Com_insert
``` 
[2013-01-22 10:56:17,950] [Thread-1] servers.diamond-test.mysql.Com_delete 0 1358848577
[2013-01-22 10:56:17,950] [Thread-1] servers.diamond-test.mysql.Com_insert 0 1358848577
[2013-01-22 10:56:17,950] [Thread-1] servers.diamond-test.mysql.Com_delete 0 1358848577
[2013-01-22 10:56:17,950] [Thread-1] servers.diamond-test.mysql.Com_insert 0 1358848577
[2013-01-22 10:56:17,951] [Thread-1] servers.diamond-test.mysql.Com_delete 0 1358848577
...
```
Fixed a small typo to get the innodb option to work ref:
https://github.com/BrightcoveOS/Diamond/blob/master/src/collectors/mysql/mysql.py#L352

I think the least privilege for running show engine innodb status is process.