Bring bosh-lite configuration up to date with recent bosh

Build a custom nginx based on the bosh release

* Create custom bosh-lite::nginx recipe
  - Use source blobs from cf-release for nginx and the required modules
  - Use modified packaging script to build nginx
  - Use nginx configuration from bosh release
* Extend cleanup to remove chef artifacts from bosh
* Update warden configuration to disable host network isolation

When combined with https://github.com/cloudfoundry/bosh-lite/pull/158, we get a functional bosh lite with an up to date bosh version (1.2697.0).