Fix dockerfile to build the new kafka output

[cpanato]

What type of PR is this?
/kind bug
/kind cleanup

Any specific area of the project related to this PR?

/area build
/area outputs

What this PR does / why we need it:

The kafka lib we are using is a wrapper of the libkafka written in C/C++ so we need to have a special build for that.

This PR fix the build image and also add a CI job to build the image to avoid issues in the future.

Also:

• Add some items in the dockerignore
• Format a bit the imports to follow the go best practices
• Add the license in the image

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[poiana]

@cpanato: The label(s) area/build, area/outputs cannot be applied, because the repository doesn't have them

In response to this:

What type of PR is this?
/kind bug
/kind cleanup

Any specific area of the project related to this PR?

/area build
/area outputs

What this PR does / why we need it:

The kafka lib we are using is a wrapper of the libkafka written in C/C++ so we need to have a special build for that.

This PR fix the build image and also add a CI job to build the image to avoid issues in the future.

Also:

• Add some items in the dockerignore
• Format a bit the imports to follow the go best practices
• Add the license in the image

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Issif

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[poiana]

LGTM label has been added.

Git tree hash: 782efeedd1ff899e5e8c857fbb4decb77edf52d9