Comment 6 for bug 1824301

Reviewed: https://review.opendev.org/655511
Committed: https://git.openstack.org/cgit/openstack/tripleo-common/commit/?id=f19863f332ca1e42c1a20462212c0a809d59241d
Submitter: Zuul
Branch: stable/stein

commit f19863f332ca1e42c1a20462212c0a809d59241d
Author: Emilien Macchi <email address hidden>
Date: Thu Apr 11 09:57:00 2019 -0400

    docker-rm: check if rpm dependency is actually installed

    If the deployment wasn't deployed under Docker, python2-docker package
    is missing. Therefore, during the upgrade we don't want to try to remove
    the containers under Docker, since they don't exist anyway.

    python2-docker is needed by Ansible to remove the containers, so let's
    make sure the package is installed, which is the case when the
    deployment was under Docker.
    If the rpm doesn't exist, we'll skip the tasks and don't try to remove
    the containers.

    The main case where docker-rm is useful is when upgrading on centos7
    from rocky to stein, since we clear containers running in Docker during
    the upgrade, so they run on Podman.

    In reality, the future platform won't have Docker installed, so this
    role will become useless and we'll probably deprecate it.

    Closes-Bug: #1824301
    Change-Id: Ic5036ffa756775e3806e18b09e034af2290bfb56
    (cherry picked from commit e368e15226b18d6f75b0ffaca424ce4cb574b2a4)