Add bread crumbs so VMs use eth1 as part of OVS bridge

With this change, I'm leaving a hint on how I can change the vms
to use tap1 as a bridged interface. That allows me to connect
the nodes to other ports in the bridge, such as ports to docker
containers.

That is used as an example in this page:
http://www.flaviof.com/blog/work/how-to-odl-in-docker.html

Note that the hypervisor is perfectly okay with having multiple
VMs on top of the same tap1 interface, so there is no need to
create tap2, tap3... etc.

Vagrantfile

@@ -26,6 +26,7 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
   config.vm.define "devstack-control", primary: true do |control|
     control.vm.box = "ubuntu/trusty64"
     control.vm.hostname = "devstack-control"
+    ## control.vm.network "public_network", ip: "#{control_ip}", bridge: "tap1"
     control.vm.network "private_network", ip: "#{control_ip}"
     ## control.vm.network "forwarded_port", guest: 8080, host: 8081
     control.vm.network "private_network", ip: "#{neutron_ex_ip}", virtualbox__intnet: "mylocalnet", auto_config: false
@@ -56,6 +57,7 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
       compute_index = n+1
       compute.vm.box = "ubuntu/trusty64"
       compute.vm.hostname = "devstack-compute-#{compute_index}"
+      ## compute.vm.network "public_network", ip: "#{compute_ip}", bridge: "tap1"
       compute.vm.network "private_network", ip: "#{compute_ip}"
       compute.vm.network "private_network", ip: "#{compute_ex_ip}", virtualbox__intnet: "mylocalnet", auto_config: false
       compute.vm.provider :virtualbox do |vb|