Clarify docker pieces for multi server setup

[collateral127]

https://doc.crowdsec.net/docs/user_guides/multiserver_setup
it'd really help if you clarified the docker environment variables you needed for a multi server setup on the agent end:

DISABLE_LOCAL_API=true
LOCAL_API_URL=http://host.ip.address:8080
AGENT_USERNAME=username
AGENT_PASSWORD="password"

The blog post you reference certainly helps, but there are a bunch of steps you'd do on bare metal that don't make sense in the context of containerisation, and would require editing the dockerfile to do.

The only other thing is that it's not immediately clear (at least it wasn't to me) that the LAPI and agent are part of the same container - when i was looking at the multi server setup initially, i was looking for an agent container I didn't need.

[LaurenceJJones]

Thank you for this feedback (I know im really late). I plan to rewrite the article and some aspects of this documentation I will keep these points in mind.