bugfix: inspect image by image id with prefix

[YaoZengzeng]

Signed-off-by: YaoZengzeng [email protected]

Ⅰ. Describe what this PR did

We should be able to get the information of the image by full image ID like :

[root@pouch-test pouch]# pouch image inspect sha256:5d9d6baef42b5850535f948d717bf71155bd4b352d392e5ca37ea95eaaac25d9
{
    "Architecture": "amd64",
    "Config": {
        "Cmd": [
            "sh"
        ],
        "Entrypoint": null,
.........

And this PR is just a quick workaround to make k8s + pouch could work ASAP, we should make it more elegant and systematic :)

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how you did it

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #895 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #895      +/-   ##
==========================================
- Coverage   14.37%   14.37%   -0.01%     
==========================================
  Files         117      117              
  Lines        7103     7104       +1     
==========================================
  Hits         1021     1021              
- Misses       5995     5996       +1     
  Partials       87       87

Impacted Files	Coverage Δ
daemon/mgr/image_utils.go	0% <0%> (ø)	⬆️

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[YaoZengzeng]

@allencloud Please merge this PR ASAP :)

[HusterWan]

LGTM