integration: use busybox:1.32.0 since latest is unavailable
integration: use busybox:1.32.0 since latest is unavailable

```bash
curl -s https://mirror.gcr.io//v2/library/busybox/tags/list | jq '[.tags ]'
[
  [
    "1.26.2",
    "1.27.2",
    "1.28",
    "1.29",
    "1.29.2",
    "1.30",
    "1.30.1",
    "1.31",
    "1.31.0",
    "1.31.1",
    "1.32.0"
  ]
]
```

The latest is gone. I think we should setup image in github container
registry for CI if possible.

Signed-off-by: Wei Fu <df4176d36abdc6fd0d966de5d5471522668de494@gmail.com>

containerd/containerd,estesp/containerd,thaJeztah/containerd,dmcgowan/containerd,vdemeester/containerd,dmcgowan/containerd,containerd/containerd,vdemeester/containerd,mikebrow/containerd,estesp/containerd,thaJeztah/containerd,mikebrow/containerd