Added node['docker']['no_proxy'] to complement the existing http_proxy attribute.

Even if little advertised, the docker daemon respects the `NO_PROXY` environment variable if present.

Setting this variable can be desirable to avoid passing through a proxy, for example when accessing a local docker registry (even more when the docker registry is running on an host that is not reachable from the http proxy such as localhost).

This PR adds a new attribute, `node['docker']['no_proxy']` which will be injected in the default docker configuration, exactly like for the `node['docker']['http_proxy']` attribute.