Pin chef server api version to 0, fixes #56

[sersut]

/cc: @stevendanna, @tyler-ball

Fixes #56
Fixes chef-boneyard/chef-provisioning#394

[sersut]

Also tested this in the context of #56 and looks like it works.

[tyler-ball]

Verified locally! Thanks so much @sersut

[aleksey-hariton]

Guys, this bugfix brokes chef-provisioning.

• cheffish 1.6.0
• chef-provisioning 1.5.0
• chef-server 12.1.2
• chef-client 12.3

  machine_batch("Queue 6") do
    action [:converge]
    driver "fog:OpenStack"
    chef_server {:chef_server_url=>"https://chefserver//organizations/ORG", :options=>{:client_name=>"haritona", :signing_key_filename=>"client.pem"}}
    declared_type :machine_batch
    machines ["frontend01"]
  end

Raises error:

Chef::Exceptions::ImmutableAttributeModification: Node attributes are read-only when you do not specify which precedence level to set. To set an attribute use code like `node.default["key"] = "value"'

Stack trace:

...gems/ruby-2.2.1/gems/chef-12.3.0/lib/chef/node/immutable_collections.rb:165:in `block (2 levels) in <class:ImmutableMash>'
...gems/ruby-2.2.1/gems/cheffish-1.6.0/lib/cheffish.rb:23:in `chef_server_api' <<<ROOT CAUSE
...gems/ruby-2.2.1/gems/cheffish-1.6.0/lib/cheffish/chef_provider_base.rb:8:in `rest'
...gems/ruby-2.2.1/gems/cheffish-1.6.0/lib/chef/provider/chef_node.rb:42:in `load_current_resource'
...gems/ruby-2.2.1/bundler/gems/chef-provisioning-65f644dffe38/lib/chef/provider/machine.rb:179:in `load_current_resource'
...gems/ruby-2.2.1/bundler/gems/chef-provisioning-65f644dffe38/lib/chef/provider/machine_batch.rb:167:in `block in load_current_resource'
...gems/ruby-2.2.1/gems/chef-12.3.0/lib/chef/chef_fs/parallelizer/parallel_enumerable.rb:267:in `call'
...gems/ruby-2.2.1/gems/chef-12.3.0/lib/chef/chef_fs/parallelizer/parallel_enumerable.rb:267:in `process_input'
...gems/ruby-2.2.1/gems/chef-12.3.0/lib/chef/chef_fs/parallelizer/parallel_enumerable.rb:257:in `process_one'
...gems/ruby-2.2.1/gems/chef-12.3.0/lib/chef/chef_fs/parallelizer.rb:93:in `call'
...gems/ruby-2.2.1/gems/chef-12.3.0/lib/chef/chef_fs/parallelizer.rb:93:in `worker_loop'

If comment this 087f683#diff-a70f0dce71a85be109b4f0cca2d8d14fR22 everything works fine.