RCO splits workforce with unmanned tunnel boring machines

[Thy Reaper]

Witnessed on latest beta branch, but the bug is probably older than that.

I have a Rail Construction Office with both a rail layer and a tunnel boring machine. This office is currently busy building out a metro line, so both machines are able to be busy most of the time. While both the track layer and tunnel borer are deployed, the track layer is only receiving half of the workforce available in the RCO (RCO shows 60 people working, track layer only shows 30), despite the tunnel boring machine not having any workforce capacity.