Remove Ubuntu Bionic specific vars file - breaks multi-arch (#3974)

roles/container-engine/docker/vars/ubuntu-bionic.yml

----
-docker_kernel_min_version: '3.10'
-
-use_docker_engine: false
-
-docker_versioned_pkg:
-  'latest': docker-ce
-  '18.03': docker-ce=18.03.1~ce-3-0~ubuntu
-  '18.06': docker-ce=18.06.1~ce~3-0~ubuntu
-  '18.09': docker-ce_18.09.1~3-0~ubuntu-{{ ansible_distribution_release|lower }}
-  'stable': docker-ce=18.06.1~ce~3-0~ubuntu
-  'edge': docker-ce=18.06.1~ce~3-0~ubuntu
-
-docker_package_info:
-  pkg_mgr: apt
-  pkgs:
-    - name: "{{ docker_versioned_pkg[docker_version | string] }}"
-      force: yes
-
-docker_repo_key_info:
-  pkg_key: apt_key
-  url: '{{ docker_ubuntu_repo_gpgkey }}'
-  repo_keys:
-    - 9DC858229FC7DD38854AE2D88D81803C0EBFCD88
-
-docker_repo_info:
-  pkg_repo: apt_repository
-  repos:
-    - >
-       deb [arch=amd64] {{ docker_ubuntu_repo_base_url }}
-       bionic
-       stable