This oneliner change allows apt-key to inherit the http_proxy variable.

Before this fix

  TASK: [apt_repository repo='ppa:vbernat/haproxy-1.5'] *************************
  failed: [134.226.115.202] => {"cmd": ["apt-key", "adv", "--recv-keys", "--keyserver", "keyserver.ubuntu.com", "CFFB779AADC995E4F350A060505D97A41C61B9CD"], "failed": true, "rc": 2}
  stderr: gpg: requesting key 1C61B9CD from hkp server keyserver.ubuntu.com
  gpg: no valid OpenPGP data found.
  gpg: Total number processed: 0

After the fix

  TASK: [apt_repository repo='ppa:vbernat/haproxy-1.5'] *************************
  changed: [134.226.115.202]