Add load-balancing support

Whilst we don't currently use a load-balancer to balance requests to the
off-site backup machine, I am adding support for load-balancing for two reasons:

1) We may need to load-balance in future, and adding support at this stages
   reduces overheads in future when we need to start balancing requests.

2) If load balancing is configured manually on the vSE (which it shouldn't be,
   but it may well happen), we will not have a version-controlled configuration.
   By providing a configuration, we can at least ensure that Jenkins is applying
   the version-controlled configuration at all times.

This commit, therefore, adds:

- the `lb` component to the `jenkins.sh` file in order to configure
  load-balancing from `vcloud-net-launch`

- a ruleset to apply using `vcloud-net-launch`