docker: add cgroupns task config

[Mongey]

Description

This is a redo of #17702

The Datadog Agent docs specifies that you should set cgroupns=host, but I can't do that via nomad.

docker run -d --cgroupns host \
    --pid host \
    --name dd-agent \
    -v /var/run/docker.sock:/var/run/docker.sock:ro \
    -v /proc/:/host/proc/:ro \
    -v /sys/fs/cgroup/:/host/sys/fs/cgroup:ro \
    -e DD_SITE=<DATADOG_SITE> \
    -e DD_API_KEY=<DATADOG_API_KEY> \
    gcr.io/datadoghq/agent:7

#17702 (comment)

Testing & Reproduction steps

Links

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[tgross]

Hi @Mongey! Thanks for this contribution.

Unfortunately this doesn't seem to compile at the moment, so it doesn't pass tests either. If you can get that patched up we'd be happy to review again.

[Mongey]

@tgross updated, sorry about that 😓

[aimeeu]

Thanks for updating the docs! I left a suggestion so the docs content matches our docs style guide.

[tgross]

LGTM!

Author accepted suggestions.

[tgross]

@Mongey this will ship in the next regular patch release for Nomad 1.10.x.