batch size finder does not recognize flag and seems to download often

[williamFalcon]

the --auto_scale_batch_size flag requires a string. But it should also just work with set_true

1. ie: support this case:

--auto_scale_batch_size

2. it seems to trigger data downloads more frequently?

Files already downloaded and verified
Files already downloaded and verified
Files already downloaded and verified
Files already downloaded and verified
Files already downloaded and verified
Files already downloaded and verified
Batch size 2 succeeded, trying batch size 4
Files already downloaded and verified