Attach eth2 of vm to OVS_PHYSICAL_BRIDGE in devstack
Remove IP from eth2 after adding interface to the bridge

Allows floating IPs to be accessible from outside the vagrant vm
Only run OVS command to add port public_interface to br-ex once
Enable neutron by default
Do not use absolute paths

Firstly, because they were wrong, and secondly because
we don't use full paths anywhere else.