Add extended IP forwarding options

As specified per the openstack training guide
http://docs.openstack.org/training-guides/content/lab003-compute-node.html

net.ipv4.ip_forward=1
net.ipv4.conf.all.rp_filter=0
net.ipv4.conf.default.rp_filter=0

Changed note about hosts file to include commenting out 127.0.1.1