CI: improve Docker setup (#550)

* Cache has already been updated a few lines before.

* When skipping Docker cleanup, create flag to avoid the expensive part of the setup (including package manager cache update) to be run again.

tests/integration/targets/setup_docker/tasks/Debian.yml

@@ -35,7 +35,6 @@
     apt:
       name: '{{ docker_packages if needs_docker_daemon else docker_cli_packages }}'
       state: present
-      update_cache: true
 
   always:
   - name: Restore /usr/sbin/policy-rc.d (if needed)

tests/integration/targets/setup_docker/tasks/main.yml

@@ -14,6 +14,13 @@
     - name: Detect whether we are running inside a container
       current_container_facts:
 
+    - name: Look for marker whether Docker was already set up
+      stat:
+        path: /root/community.docker-docker-is-set-up
+      register: docker_setup_marker
+
+    - when: not docker_setup_marker.stat.exists
+      block:
         - name: Determine whether Docker Daemon needs to be installed
           set_fact:
             needs_docker_daemon: '{{ not ansible_module_running_in_container }}'
@@ -49,6 +56,12 @@
             state: started
           when: not ansible_module_running_in_container
 
+        - name: Set marker that Docker was already set up
+          file:
+            path: /root/community.docker-docker-is-set-up
+            state: touch
+          when: docker_skip_cleanup
+
     # Detect docker API version
     - name: Check Docker API version
       command: "docker version -f {% raw %}'{{(index .Server.Components 0).Details.ApiVersion}}'{% endraw %}"