Fix parsing Docker scan flags and Args

[attiasas]

• All tests have passed. If this feature is not already covered by the tests, new tests have been added.
• The pull request is targeting the master branch.
• The code has been validated to compile successfully by running go vet ./....
• The code has been formatted properly using go fmt ./....

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Depends on:

• Convert flags public jfrog-cli-core#1507

Note: There is still an issue parsing flags/arguments.
This PR only fixing that the inner docker scan cmd flags will be parsed as flags and not arguments.
For the scan to work you need to run: docker scan <img> [flags] (argements before flags)

[github-actions]

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🐸 JFrog Frogbot

[RemiBou]

no test ?

[RemiBou]

why not use flagNames in the whole method and then convert it to slice ?