[Docker Plug-in] Don't pull image if already exists unless forced

[mocsharp]

Description

In many use cases, users may build their images locally first and therefore, the Docker Plug-in would fail because it always tries to pull the image.

This PR checks the existence of the image first and will not attempt to pull the image unless the user asks for it by setting it in the workflow definition:

{
   "always_pull": "true"
}

Status

Ready

Types of changes

• [x] Non-breaking change (fix or new feature that would not break existing functionality).
• [ ] Breaking change (fix or new feature that would cause existing functionality to change).
• [ ] New tests added to cover the changes.
• [x] All tests passed locally.
• [ ] Documentation comments included/updated.
• [ ] User guide updated.
• [ ] I have updated the changelog

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

100.0% Coverage
0.0% Duplication

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