Remove bgp-vpn from scenario004-multinode-containers

Remove bgp-vpn from scenario004-multinode-containers

See full context on https://bugs.launchpad.net/bugs/1713612
but this service isn't containerized yet, so the plan is:

- in Pike, we'll run scenario004 (baremetal) and test bgp-vpn and l2gw
- in Queens, we'll run scenario004 (baremetal at the beginning) but
  scenario004-container will be the default and we'll re-add the 2
  services when containerized.

Change-Id: I04c2a9fb63420b7d8d3616a8ef7a50d2aadc6165
(cherry picked from commit fde4ff2c64f374e109dbb7da87cc7d72da5e0ef5)