Guards of execute resource doesn't inherit command options from its parent resource

* Replaces https://github.com/opscode/chef/pull/2105.
* Removes `path` attribute from `execute` resource which is never backed by any logic.
* Adds a new guard interpreter for execute resource that can inherit :cwd and :environment from the original resource. 

There is an open question of: 
```
# TODO: Do we want to also get :group, :user, :umask ?
```

/cc: @opscode/client-engineers 

Nice catch.