Add Molecule to Docker role (#5129)

* Add Molecule for container-engine/docker

* Add bootstrap-os to Molecule prepare stage

roles/container-engine/docker/molecule/default/molecule.yml

@@ -0,0 +1,29 @@
+---
+driver:
+  name: vagrant
+  provider:
+    name: libvirt
+lint:
+  name: yamllint
+  options:
+    config-file: ../../../.yamllint
+platforms:
+  - name: kubespray-docker
+    box: generic/ubuntu1804
+    cpus: 2
+    memory: 1024
+provisioner:
+  name: ansible
+  env:
+    ANSIBLE_ROLES_PATH: ../../../../
+  config_options:
+    defaults:
+      callback_whitelist: profile_tasks
+  lint:
+    name: ansible-lint
+    options:
+      c: ../../../.ansible-lint
+verifier:
+  name: testinfra
+  lint:
+    name: flake8