The capability to handle a variance between prod and staging
here is just temporary while I'm testing the new fixed asset
handling stuff by deploying it on staging. Once it's tested
and merged we'll just have prod and staging do the same thing.
But for now we need to cleanly handle them having the static
disk images in different places.
instead of just relying on it getting run when we do an
ansible run, since that's intermittent and it's annoying
when you want to do an ansible run and it sits there for
hours creating disk images. This way we'll know they'll
get updated regularly and ansible runs should never get
blocked on image creation, though we still do it in the
ansible plays just in case (and for initial deployment).
This should now be safe, with the recent changes to make it
time out gracefully and run atomically. We also use withlock
to make sure we don't stack jobs.
