fix(docker): build healthcheck command when building dockerfile from image config

[DmitriyLewen]

Description

There are cases when HEALTHCHECK in image config doesn't have /bin/sh prefix.
e.g.
Dockerfile:

FROM alpine

HEALTHCHECK --interval=10s --timeout=3s CMD curl --fail http://localhost:3000 || exit 1 

Image history:

➜ docker history 3814 
IMAGE          CREATED        CREATED BY                                      SIZE      COMMENT
b3bcbd9f64be   7 months ago   HEALTHCHECK &{["CMD-SHELL" "curl --fail http…   0B        buildkit.dockerfile.v0
<missing>      7 months ago   /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B        
<missing>      7 months ago   /bin/sh -c #(nop) ADD file:2a949686d9886ac7c…   5.54MB  

We are currently skipping this line and getting a false positive.

Related issues

• Close Docker image compliance scan, docker-cis: false positives #3814

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).