Add deleting created LBs to cloudcafe cleanup job

The cloudcafe tests create load balancers which may not get cleaned up, and there is a hard limit to the number of load balancers per account.  Add deleting load balancers to the cleanup job.

This doesn't go through any of the cloudcafe auto-marshalling, and just munges the JSON manually, since everything in cloudcafe may change due to an upgrade and I don't want to cause incompatibility problems.

Too many load balancers on the account have been causing test failures in jenkins - hopefully this should reduce them a bit.
:open_mouth: