Support and expand Buildbot's ability to interact with virtual workers. Current support:
- and more..
- Latent build slaves shut down uncleanly and get forgotten by the master
- start_instance on a latent BuildSlave called before stop_instance finished
- Buildbot doesn't terminate latent EC2 servers upon shutdown
- LatentSlaveBuilder status does not get reset to LATENT when detached
- Flexibility to Stop or Terminate LatentSlave as load drops