[REVIEW-ONLY] puppet api extension

Changed puppet data source from ralph-db to defined chain, which is this:
The chain:
- try get data from puppetdb-api
- then try get data from ralph-db

@andrzej-jankowski 
Could you review it, please?
When ``PUPPET_API_JSON_CERTS`` is not defined you should also raise ``PuppetConfigurationError`` exception...