Fix permission error when using local storage for droplets

* Local directory for droplet(without NFS) in CC should be created and chown to vcap
* Nginx config for local root should not be hardcoded


when we use local_provider for cc droplet without an NFS job. (we use this in a local warden-cpi deploy)
the local_root directory was never created and chown to vcap, which will result in a permission denied error.

also for the nginx configuration, the local_root directory should not be hardcoded to /var/vcap/shared, since we provide properties to control it.

@mkocher 
story here: https://www.pivotaltracker.com/story/show/54080607