GC remove current running image related task data

[ppancake]

Bug report:

GC remove current running image associated task data

Expected behavior:

When triggering GC, retain tasks data associated with running images.

How to reproduce it:

Set up a local cluster using kind and configured the /var/lib/dragonfly data directory in dfget.yaml to be 50M in size. I started a custom BusyBox pod, and observed task data in the directory. Then, I pulled multiple images, causing the directory size to exceed 50M, which triggered GC. After the GC, I found that the /var/lib/dragonfly directory was emptied. Looking at the TryGC code block, the task.Done is cleaned up. The data for the BusyBox was marked as done after the pull was completed. I hope that tasks for images that are still running are not cleaned up.

Environment:

• Dragonfly version: v2.1.0
• OS: 22.04.1-Ubuntu
• Kernel (e.g. uname -a): Linux kind-worker 6.8.0-47-generic 47~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Oct 2 16:16:55 UTC 2 x86_64 GNU/Linux
• Others:

[gaius-qi]

@ppancake Please use English, thanks.