Fix baremetal role idempotency

When you add new nodes to existing cluster, docker will restart
all anyway and that will break a lot, including mariadb.

Change-Id: Ie46f99a141f99480a87218ead4b76ba65f2edae9
Closes-Bug: #1699335

ansible/roles/baremetal/tasks/post-install.yml

@@ -15,6 +15,7 @@
     dest=/etc/systemd/system/docker.service.d/kolla.conf
   when: (ansible_distribution == "Ubuntu" and ansible_distribution_major_version > "14") or
         (ansible_os_family == "RedHat") or (ansible_distribution == "Debian")
+  register: docker_configured
 
 - name: Reload docker service file
   become: True
@@ -70,6 +71,7 @@
     name: docker
     state: restarted
   become: True
+  when: docker_configured.changed
 
 - name: Enable docker
   service: