Add json_attributes: true config option to ChefZero provisioner.

[fnichol]

This option allows a user to invoke chef-client without passing the
generated JSON file in the --json-attributes option. That way if you
have a JSON definition of your node (including a run-list), the
chef-client run will depend entirely on what is on the "Chef Server".

For example, let's assume we want a node called "mynode" to be in the
"production" chef environment. Given a .kitchen.yml with the following:

---
driver:
  name: vagrant

provisioner:
  name: chef_zero
  json_attributes: false
  client_rb:
    node_name: mynode

platforms:
  - name: ubuntu-12.04

suites:
  - name: default

and an environment JSON description for our chef environment called
"production" in test/integration/environments/production.json that
looks like:

{
  "name": "production",
  "default_attributes": {
    "myenv_attr": "Good to be in prod"
  }
}

and a node JSON description for our node called "mynode" in
test/integration/nodes/mynode.json that looks like:

{
  "id": "mynode",
  "chef_environment": "production",
  "run_list": [
    "recipe[nginx]"
  ],
  "normal": {
    "some_attr": "hello"
  },
  "automatic": {
    "ipaddress": "192.168.77.77"
  }
}

then the instance will attempt to register with the Chef Zero server as
"mynode" (vs. "default-ubuntu-1204" in this case) and will receive a
run-list of ["recipe[nginx]"] from the server. Additionally the
following node attributes will be setup:

• node[:some_attr] will be set to "hello"
• node[:myenv_attr] will be set to "Good to be in prod"
• node[:ipaddress] will be set to "192.168.77.77"

Note that the node JSON format assumes a Chef 11 serialized format which
Chef Zero will use under the hood. For more details, please read:

http://docs.opscode.com/essentials_node_object.html

[spheromak]

ah this is great ⭐

[fnichol]

How did I forget about you, oh cool feature? Let's get you merged in, shall we?