CentOS build should mount cgroups and run privileged

.travis.yml

@@ -1,7 +1,17 @@
 sudo: required
 env:
-  - container_id=$(mktemp) distribution=centos version=7     init=/usr/lib/systemd/systemd
-  - container_id=$(mktemp) distribution=ubuntu version=14.04 init=/sbin/init
+  - >
+    container_id=$(mktemp)
+    distribution=centos
+    version=7
+    init=/usr/lib/systemd/systemd
+    run_opts="--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
+  - >
+    container_id=$(mktemp)
+    distribution=ubuntu
+    version=14.04
+    init=/sbin/init
+    run_opts=""
 
 services:
   - docker
@@ -19,7 +29,7 @@ script:
   #
 
     # Run container in detached state
-  - sudo docker run --detach ${distribution}:ansible "${init}" > "${container_id}"
+  - sudo docker run --detach ${run_opts} ${distribution}:ansible "${init}" > "${container_id}"
 
     # Syntax check
   - sudo docker exec "$(cat ${container_id})" ansible-playbook /etc/ansible/test.yml --syntax-check