install-docker: allow removal of conflicting packages

Allow us to define which packages need to be removed before installing
the desired ones.

Fixes use of role on systems where it was desired to install upstream
docker but the system one was already installed.

Change-Id: Ib6ae0a8fba937901b29565e2d36486eccf4f67bb

roles/install-docker/README.rst

@@ -68,6 +68,14 @@ An ansible role to install docker and configure it to use mirrors if available.
    installed prior to installing docker-ce. If the package set needs to
    be changed this option can be overridden as needed.
 
+.. zuul:rolevar:: docker_upstream_distro_remove_packages
+   :default: list
+
+   List of packages to be removed before installing new ones. It is used
+   for avoiding potential conflicts. For example it can remove `docker`
+   package before trying to install `docker-ce`. The default value is
+   distro specific.
+
 .. zuul:rolevar:: docker_upstream_distro_packages
    :default: list
 

roles/install-docker/defaults/main.yaml

@@ -8,6 +8,7 @@ docker_distro_packages: "{{ _docker_distro_packages | default([]) }}"
 docker_compose_install: false
 docker_upstream_distro_packages: "{{ _docker_upstream_distro_packages | default([]) }}"
 docker_upstream_distro_required_packages: "{{ _docker_upstream_distro_required_packages | default([]) }}"
+docker_upstream_distro_remove_packages: "{{ _docker_upstream_distro_remove_packages | default([]) }}"
 docker_update_channel: stable
 docker_download_fqdn: download.docker.com
 docker_mirror_base_url: "{{ _docker_mirror_base_url | default('') }}"

roles/install-docker/tasks/upstream-package-installation.yaml

@@ -1,4 +1,10 @@
 ---
+- name: Remove packages
+  package:
+    name: "{{ docker_upstream_distro_remove_packages }}"
+    state: absent
+  when: docker_upstream_distro_remove_packages
+
 # package/dnf module do not support `--nobest` option which is needed for
 # installing docker-ce on centos-8
 - name: Install upstream docker using package

roles/install-docker/vars/debian.yaml

@@ -14,6 +14,9 @@ _docker_upstream_distro_packages:
   - docker-ce-cli
   - containerd.io
 
+_docker_upstream_distro_remove_packages:
+  - docker.io
+
 docker_distro_vars_loaded: true
 
 _docker_mirror_base_url: "https://{{ docker_download_fqdn }}/linux/debian"

roles/install-docker/vars/fedora.yaml

@@ -11,6 +11,9 @@ _docker_upstream_distro_packages:
   - docker-ce-cli
   - containerd.io
 
+_docker_upstream_distro_remove_packages:
+  - docker
+
 docker_repo_template: docker-ce-fedora.repo.j2
 
 docker_distro_vars_loaded: true