docker checkpoint rm does not actually remove the checkpoint files.

[Yongqi-Zhuo]

Description

docker checkpoint rm does not remove the checkpoint files. For example, the current implementation uses /tmp/ctrd-checkpoint* as the fallback checkpoint directory. (code) In practice several thousand checkpoints will use up all the disk storage due to tmpfs being swapped to the disk.

Steps to reproduce the issue

1. docker checkpoint create CONTAINER ckpt --leave-running
2. docker checkpoint rm CONTAINER ckpt
3. Repeat this a few times and take a look at your /tmp.

Describe the results you received and expected

All the checkpoint files remain despite the docker checkpoint rm

What version of containerd are you using?

containerd containerd.io 1.6.31 e377cd5

Any other relevant information

No response

Show configuration if it is related to CRI plugin.

No response