Use xenial repo for ubuntu18

roles/docker/vars/ubuntu-bionic.yml

 ---
 docker_kernel_min_version: '3.10'
-docker_version: 18.06
+
 use_docker_engine: false
 
 docker_versioned_pkg:
   'latest': docker-ce
+  '17.03': docker-ce=17.03.2~ce-0~ubuntu-xenial
   '18.03': docker-ce=18.03.1~ce-3-0~ubuntu
   '18.06': docker-ce=18.06.1~ce~3-0~ubuntu
   'stable': docker-ce=18.06.1~ce~3-0~ubuntu
@@ -26,6 +27,6 @@ docker_repo_info:
   pkg_repo: apt_repository
   repos:
     - >
-       deb {{ docker_ubuntu_repo_base_url }}
-       {{ ansible_distribution_release|lower }}
-       stable
+       deb [arch=amd64] {{ docker_ubuntu_repo_base_url }}
+       xenial
+       stable
\ No newline at end of file