bugfix: use the stable image ID in test

[fuweid]

Signed-off-by: Wei Fu fhfuwei@163.com

Ⅰ. Describe what this PR did

The busybox:1.28 has been repushed so that the imageID will be changed.
In order to make the test stable, we should use the stable image.

Ⅱ. Does this pull request fix one issue?

NONE

Ⅲ. Describe how you did it

NONE

Ⅳ. Describe how to verify it

NONE

Ⅴ. Special notes for reviews

[Letty5411]

LGTM

[codecov-io]

Codecov Report

Merging #1397 into master will increase coverage by 22.27%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #1397       +/-   ##
===========================================
+ Coverage   16.28%   38.55%   +22.27%     
===========================================
  Files         198      248       +50     
  Lines       13470    16516     +3046     
===========================================
+ Hits         2193     6368     +4175     
+ Misses      11126     9328     -1798     
- Partials      151      820      +669

Impacted Files	Coverage Δ
cri/v1alpha1/service/cri.go	0% <0%> (ø)
storage/volume/modules/tmpfs/tmpfs.go	16.39% <0%> (ø)
pkg/serializer/serialize.go	9.52% <0%> (ø)
storage/volume/driver/context.go	8.69% <0%> (ø)
storage/volume/modules/ceph/types.go	0% <0%> (ø)
storage/volume/core_util.go	19.73% <0%> (ø)
cri/stream/errors.go	0% <0%> (ø)
cri/stream/remotecommand/attach.go	0% <0%> (ø)
registry/auth_challenge.go	62.5% <0%> (ø)
storage/volume/core.go	37.13% <0%> (ø)
... and 112 more