fix: 🐛 Add special case were registry is defined for library image

[daniel-anova]

What type of PR is this?

/kind bug

What this PR does / why we need it:

This handles a special case when a library image is defined while still having docker.io domain defined.

Example: docker.io/bash:latest

Which issue(s) this PR fixes:

Fixes #119

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

- handle docker library images correctly when domain is defined

Additional documentation e.g., usage docs, etc.: