Remove usage of `tf.io.gfile.glob` in CheckpointManager.
Remove usage of `tf.io.gfile.glob` in CheckpointManager.

This fix is due to @amitport on Github in PR #1. Thank you for your contribution.

PiperOrigin-RevId: 335478370
Change-Id: I57fcb551bbaf2527814a0d109906d5af4a734ff3

google-research/federated,google-research/federated