devstack: use cgroupfs driver for both docker and k8s on Cent OS

This is required for resource limiting for non-image functions as we use
the cgroup paths setup by the cgroupfs driver.

Change-Id: I91c50d5ee70a5973f720fd13c6c6214c7361fb7a

tools/gate/kubeadm/playbook/roles/docker/tasks/centos.yml

@@ -20,25 +20,7 @@
          docker-ce-17.03.2.ce-1.el7.centos \
          docker-ce-selinux-17.03.2.ce-1.el7.centos
 
-- name: Ensure docker.service.d directory
-  file:
-    path: /etc/systemd/system/docker.service.d
-    recurse: yes
-    state: directory
-
-- name: Change docker cgroup driver
-  copy:
-    content: |
-      [Service]
-      ExecStart=
-      ExecStart=/usr/bin/dockerd --exec-opt native.cgroupdriver=systemd
-    dest: /etc/systemd/system/docker.service.d/10-docker-kubeadm.conf
-    mode: 0644
-    group: root
-    owner: root
-
-- name: Restart docker service
+- name: Start docker service
   systemd:
     name: docker
-    daemon_reload: yes
-    state: restarted
+    state: started

tools/gate/kubeadm/playbook/roles/k8s_cli/tasks/centos.yml

@@ -21,3 +21,16 @@
     - kubelet-1.9.3
     - kubectl-1.9.3
     - kubeadm-1.9.3
+
+# On CentOS 7, the kubeadm package adds a configuration file that overrides
+# kubelet's cgroup driver to systemd, we want to use the default driver
+# cgroupfs to get the same cgroup paths for resource limiting.
+#
+#   $ rpm -qf /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
+#   kubeadm-1.9.3-0.x86_64
+#
+- name: Change kubelet cgroup driver
+  replace:
+    path: /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
+    regexp: '(KUBELET_CGROUP_ARGS=)[^"]+'
+    replace: '\1'