Configurable docker yum repos, systemd fix

* Make yum repos used for installing docker rpms configurable
* TasksMax is only supported in systemd version >= 226
* Change to systemd file should restart docker

roles/docker/tasks/systemd.yml

@@ -10,11 +10,17 @@
     dest: /etc/systemd/system/docker.service.d/http-proxy.conf
   when: http_proxy is defined or https_proxy is defined or no_proxy is defined
 
+- name: get systemd version
+  command: rpm -q --qf '%{V}\n' systemd
+  register: systemd_version
+  when: not (ansible_os_family in ["CoreOS", "Container Linux by CoreOS"] or is_atomic)
+
 - name: Write docker.service systemd file
   template:
     src: docker.service.j2
     dest: /etc/systemd/system/docker.service
   register: docker_service_file
+  notify: restart docker
   when: not (ansible_os_family in ["CoreOS", "Container Linux by CoreOS"] or is_atomic)
 
 - name: Write docker.service systemd file for atomic