Add vagrantfile/environment for a working vagrant all-in-one using
nova-network

Implements: blueprint reference-havana-vagrant

- remove unused attrs from previous example vagrant.rb, and change to
  vagrant-aio-nova.json
- add Vagrantfile-aio-nova targeted specifically at an allinone using
  nova-network (other vagrantfiles can cover other deployments)
- Update CentOS box to 6.5
- Remove Vagrantfile and environments/vagrant.rb to avoid confusion
- allow multiple simultaneous vagrant up with different chef-zero
  servers
- add usage comments at top of file

Change-Id: I9e4145dd1f22efa7e423794bb122bde756884f40
Merge "Add vagrantfile/environment for a working vagrant all-in-one using nova-network"