docker: simplify, use dist-based vars

roles/docker/defaults/main.yml

@@ -0,0 +1,4 @@
+---
+docker_pkgs:
+  Ubuntu: docker.io
+  Fedora: moby-engine

roles/docker/tasks/main.yml

@@ -1,32 +1,13 @@
 ---
+# depends on create-user role / create_username var
 
-- name: install docker
-  package:
-    name: docker
-    state: latest
-  when: ansible_distribution in ["CentOS", "Fedora", "Red Hat Enterprise Linux", "RedHat"] and not is_atomic
-  register: docker_installed
+- name: "Install Docker"
+  ansible.builtin.package:
+    name: "{{ docker_pkgs[ansible_distribution] }}"
+    state: present
 
-- name: add {{ username }} to 'dockerroot' group
-  user:
-    name: "{{ username }}"
-    groups: dockerroot
-    append: yes
-  when: ansible_distribution in ["CentOS", "Red Hat Enterprise Linux", "RedHat"] and not is_atomic
-
-
-- name: copy daemon.json
-  copy:
-    src: roles/docker/files/daemon.json
-    dest: /etc/docker/daemon.json
-    owner: root
-    group: root
-    mode: 0644
-  when: ansible_distribution in ["CentOS", "Red Hat Enterprise Linux", "RedHat"] and not is_atomic
-
-- name: enable/start docker
-  service:
+- name: Enable/start docker
+  ansible.builtin.service:
     name: docker
     state: started
-    enabled: yes
-  when: ansible_distribution in ["CentOS", "Fedora", "Red Hat Enterprise Linux", "RedHat"] and not is_atomic
+    enabled: true