QUEUE_HOST / QUEUE_PORT give cryptic errors when undefined

Trying to connect be like

~/P/C/build ❯❯❯ ./ContainerBuilderClient ../ContainerBuilderTitan.def poop.img
Attempting to connect to BuilderQueue:  Failed to build container: QUEUE_HOST: Operation not supported

same for QUEUE_PORT. The client should complain in a more straight-forward way if they are missing (though I reckon this will be deployed via environment modules that would set these variables anyhow?)