Add proxy config to standalone container registry

[nuka137]

Current standalone container registry can not work on the proxy environment.
This PR enables us to specify the proxy configurations for standalone container registry.

[ajdecon]

@nuka137 : This looks reasonable to me!

Can you please sign off on your commit as detailed in our CONTRIBUTING.md doc? And then I can merge the PR.

[nuka137]

@ajdecon

Recommitted about previous patch.
Could you check it?

[ajdecon]

This actually appears to fail in the default case (without a proxy). If the variable isn't defined, Ansible won't run.

We use a different pattern in other tasks (example) that looks like this:

- name: apt install pciutils
  apt: name=pciutils update_cache=yes
  when: ansible_os_family == 'Debian'
  environment: "{{ proxy_env if proxy_env is defined else {} }}"

And then define proxy_env if needed:

# proxy_env:
      # http_proxy: '{{ http_proxy }}'
      # https_proxy: '{{ https_proxy }}'
      # no_proxy: '{{ no_proxy }}'

Can you convert this to either use the same proxy_env variable, or a similar pattern that works when no proxy is present?

[nuka137]

@ajdecon

Thanks. I fixed it.

[ajdecon]

LGTM