Add gre mode support to Quantum. [2/4]

This pull request does the following things:

 * Clean up interface creation on quantum and nova nodes, mostly by
   not creating any interfaces we don't have to.
 * Stop creating a helper route to get to the quantum metadata
   server.  We have a working metadata proxy, so it just interferes
   with the other networking mode.
 * Add support for running quantum in GRE tunnelling mode.  This
   requires a dedicated network (named os_sdn (as in openstack
   software defined network)) seperate from the other networks.  The
   default network config for os_sdn in the network.json looks like
   this:
          "os_sdn": {
              "conduit": "intf1",
              "vlan": 700,
              "use_vlan": true,
              "add_bridge": false,
              "subnet": "192.168.130.0",
              "netmask": "255.255.255.0",
              "broadcast": "192.168.130.255",
              "ranges": {
                  "host": { "start": "192.168.130.10", "end": "192.168.130.254"}
              }
          },
   This network is what Quantum uses to tie the OVS switches together
   with GRE tunnels.
 * Modify the Nova smoketest to only operate with floating IP
   addresses.  When Quantum is running in GRE mode, it is not possible
   without doing something extremly foolish for a tenant network to
   talk directly with the outside world.
   


 chef/data_bags/crowbar/bc-template-network.json |   12 ++++++++++++
 1 file changed, 12 insertions(+)

Crowbar-Pull-ID: c9539d81711c2214b06995a82fd0ca64896a1732

Crowbar-Release: pebbles