Update docker for CentOS issues in AWS and general

variables.

1. AWS has issues with ext4 (use xfs instead for CentOS only)
2. Make sure all the centos config files are include in the systemd config
3. Make sure that network options are set in the correct file by os family

This allows downstream items like opencontrail and others change variables
in expected locations.

roles/network_plugin/tasks/main.yml

@@ -10,7 +10,7 @@
 - name: Set docker daemon options
   template:
     src: docker
-    dest: "/etc/default/docker"
+    dest: "{{ '/etc/sysconfig/docker-network' if ansible_os_family == 'RedHat' else '/etc/default/docker' }}"
     owner: root
     group: root
     mode: 0644