b975102633
Fix a race condition here:
with self.learn.no_bar(), self.learn.no_logging():
dl = self.learn.dls.test_dl(files, bs=bs)
batch, _ = self.learn.get_preds(dl=dl)
The calls to `no_bar()` and maybe `no_logging()` were unsafe in a
multithreaded environment because they modified the shared `self.learn`
object. This led to random exceptions and deadlocks when gunicorn was
under load in production.