Force a checkpoint immediately after sky setup and before the object loop

[cwwalter]

There is a fair amount of time used during sensor visit setup including drawing the sky etc. If we checkpointed right after this point (instead of waiting for a few hundred objects to be drawn) we could always start directly drawing objects if the job times out. In this scenario only in the case where a single object couldn't be drawn in a normal job time could we wind up with non-completing jobs.

[cwwalter]

This issue closed by lsst-sims/legacy_sims_GalSimInterface#66