PathManager has no attribute `supports_rename`

Created by: andrewPoulton

🐛 Bug

Following #441, a regression occurs when running metaseq/launcher/opt_baselines.py, due to the call to PathManager.supports_rename on L536 in checkpoint_utils.py, but this attribute no longer exists after #441 was merged.

To Reproduce

Run (eg from @Xirider)

python metaseq/launcher/opt_baselines.py --prefix train.8m --model-size 8m --checkpoints-dir ./test-checkpoint --tensorboard-logdir ./test-checkpoint --num-trials 1 --azure --num-gpus 4 --num-nodes 1 --seed 1 --circleci --local --disable-validation --max-epoch 100 --max-update 100