Issue #16 : chef-init doesn't adopt orphaned child

Code for cleaning up terminated process.
See issue https://github.com/opscode/chef-init/issues/16 for details.
It is just style, but since we aren't using the exception here, we can consolidate this to

```
rescue Errno::ECHILD, Errno::ESRCH
  return
```

If we remove 309-311 as I believe we can, it creates a much simpler little block to follow.