Ensure ip_forward set before Docker
Ensure ip_forward set before Docker

Docker will attempt to configure iptables rules if it finds that
ip_forward is not enabled prior to the docker daemon getting started.
We should ensure that this gets configured prior to Docker being
configured if we are configuring it with puppet.

Change-Id: I6ea6fb8ed300d284c961e7474ff84d104f326255
Needed-By: I557e4a41c4e5be3a2f50e5d5ddc86e17c1eb44e1
Related-Bug: #1750194

openstack/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo