update /etc/hosts and system level

Change-Id: If14e63ad26c5a3fc915680c8e3569dfba526297a
diff --git a/classes/cluster/virtual-mcp11-ovs-ironic/openstack/init.yml b/classes/cluster/virtual-mcp11-ovs-ironic/openstack/init.yml
index 2cc6792..45b8a3c 100644
--- a/classes/cluster/virtual-mcp11-ovs-ironic/openstack/init.yml
+++ b/classes/cluster/virtual-mcp11-ovs-ironic/openstack/init.yml
@@ -93,6 +93,7 @@
     linux_system_repo: 'deb [arch=amd64] http://mirror.fuel-infra.org/mcp-repos/ocata/xenial ocata main'
   linux:
     network:
+      purge_hosts: true
       host:
         prx:
           address: ${_param:openstack_proxy_address}