Enable the service by default on Debian

In order to run the sysstat at system start and enabling the collection of performance data you need to change the ```ENABLED``` parameter to ```true``` in ```/etc/default/sysstat```

This can be simply done with augeas:  
```augeas { '/etc/default/sysstat':
    context => '/files/etc/default/sysstat/',
    changes => 'set ENABLED true',
    require => Package['sysstat'],
  }```