Add support to deployment group agents

[cnatan]

Add support to a new kind of vsts agent: https://docs.microsoft.com/en-us/vsts/build-release/concepts/definitions/release/deployment-groups/?view=vsts

Also add support to installations setted up behind a http proxy.

Made a fix to distro check, In ansible 2.5.0 the ansible_distribution_ facts return the following:

       {
        "ansible_distribution": "RedHat",
        "ansible_distribution_file_parsed": true,
        "ansible_distribution_file_path": "/etc/redhat-release",
        "ansible_distribution_file_search_string": "Red Hat",
        "ansible_distribution_file_variety": "RedHat",
        "ansible_distribution_major_version": "7",
        "ansible_distribution_release": "Maipo",
        "ansible_distribution_version": "7.5"
      }