Include containernetworking-plugins in ubuntu deps

[smartin015]

Not including the containernetworking-plugins package on Ubuntu Server 20.04 LTS gives the following error when building and running from source:

WARN[0001] Failed to load cached network config: network podman not found in CNI cache, falling back to loading network podman from disk 
WARN[0001] 1 error occurred:
        * plugin type="tuning" failed (delete): failed to find plugin "tuning" in path [/usr/local/libexec/cni /usr/libexec/cni /usr/local/lib/cni /usr/lib/cni /opt/cni/bin]
 
Error: plugin type="bridge" failed (add): failed to find plugin "bridge" in path [/usr/local/libexec/cni /usr/libexec/cni /usr/local/lib/cni /usr/lib/cni /opt/cni/bin]

After sudo apt -y install containernetworking-plugins, this message goes away and I can sucessfully start a container.

[Luap99]

For newer podman versions we should use netavark and aardvark-dns and only fall back to cni if that is not installed.
So I think it would make more sense to list those over the cni plugins.

[TomSweeneyRedHat]

@smartin015 thanks for the PR. @lsm5 just updated this same document pretty significantly. I'm not sure you got his changes or not. Lokesh, thoughts?

I concur with @Luap99 , we're moving away from CNI, we should talk about netavark/aardvark-dns unless we're talking about old versions of the code (Podman 3.* and below)

[lsm5]

hmm, do we even have nv / av on 20.04 LTS? https://launchpad.net/ubuntu/+source/netavark

Maybe we'll need separate sections for nv/av and cni ?

[lsm5]

@smartin015 could you please revise your PR to add a separate section for ubuntu 20.04 below the current ubuntu section? We would prefer not to mention cni unless required. Thanks.

[lsm5]

@smartin015 also, please sign your commit to get the DCO task successful. See: https://github.com/containers/podman.io/pull/201/checks?check_run_id=16176897846

[lsm5]

closing this in favour of #206.