Merge pull request #71 from yankcrime/groups_fix

Update user's supplementary group membership, not primary group

tasks/docker-users.yml

@@ -2,6 +2,6 @@
 - name: Ensure docker users are added to the docker group.
   user:
     name: "{{ item }}"
-    group: docker
+    groups: docker
     append: yes
   with_items: "{{ docker_users }}"