[kubernetes] Add DebianPlugin to plugin kubernetes

[jcastill]

Add DebianPlugin to the list of imports and
the class UbuntuKubernetes.

Related: #3484

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[packit-as-a-service]

Congratulations! One of the builds has completed. 🍾

You can install the built RPMs by following these steps:

• sudo yum install -y dnf-plugins-core on RHEL 8
• sudo dnf install -y dnf-plugins-core on Fedora
• dnf copr enable packit/sosreport-sos-3485
• And now you can install the packages.

Please note that the RPMs should be used only in a testing environment.

[pmoravec]

Nice catch.