handle template default for @process_manager properly

otherwise can end up with some parameters missing:

```
[12-Dec-2013 15:03:16] ALERT: [pool www] pm.min_spare_servers(0) must be a positive value
[12-Dec-2013 15:03:16] ERROR: failed to post process the configuration
[12-Dec-2013 15:03:16] ERROR: FPM initialization failed
```
this template default value should be really done from lrwp, not inside template