Parallel job generation causes wagons to be assigned to multiple jobs

[fauxnik]

Triggering job generation via Comms Radio causes job generation to happen in parallel when multiple stations are listed. This happens for stations that are located close together, like Machine Factory and Machine Factory Military Base. When this occurs, each involved wagon ends up being assigned to multiple jobs because the check for job assignment only happens at the beginning of the process.

[fauxnik]

Perhaps this could be solved by placing a mutex lock around the job generation algorithm?