Support proxy config for newer GPG

[Yang Youseok]

From newer gnu gpg (https://bugs.launchpad.net/ubuntu/+source/gnupg2/+bug/1625848), apt-key does not accept environment variable for security reason.

It blocks building image at 'apt-key add' step behind proxy environment.

I think it's better to add --keyserver-option http-proxy=URL when http_proxy variable is defined at Dockerfile.

Thanks.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/692029

[Marcin Juszkiewicz (hrw)]

rewrote patch to fit current master

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/kolla/+/692029
Committed: https://opendev.org/openstack/kolla/commit/c0c2076c856975e83a624eb793b586f2a4354a7f
Submitter: "Zuul (22348)"
Branch: master

commit c0c2076c856975e83a624eb793b586f2a4354a7f
Author: Yang Youseok <email address hidden>
Date: Wed Oct 30 14:35:14 2019 +0900

    Add HTTP proxy support for fetching APT keys

    In network isolated environments the only way to go outside is through
    HTTP proxy. Make use of it if set.

    Co-authored-by: Marcin Juszkiewicz <email address hidden>

    Closes-Bug: #1850575
    Change-Id: I2718884c4742cb81a3900e38fee62fbd27b472d7

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/kolla 14.0.0.0rc1 release candidate.