Add a quick guide for setting up the remote (and LXC) spawners

[pevogam]

Let's reuse @wsakernel's effort in documenting some crucial steps for a new user of the remote (and LXC) spawners. Instructions are as follows:

First add the slot to your avocado config file:

    [spawner.remote]
    slots = ['board']

Then you need a JSON file of the same name as the slot. Its contents are the command line parameters of the remote_login function of class remote, e.g.:

    {
        "client": "telnet",
        "host": "192.168.64.2",
        "port": "23",
        "username": "root",
        "password": "",
        "prompt": "#"
    }

Final important detail: the remote site also needs avocado installed.

[pevogam]

I am mostly leaving this for the future where we improve some of the new user experience before @wsakernel's output gets lost deep in the comments of a merged pull request.

[clebergnu]

I am mostly leaving this for the future where we improve some of the new user experience before @wsakernel's output gets lost deep in the comments of a merged pull request.

Thanks for this @pevogam. I've added your text as close to verbatim as possible to #5846

[pevogam]

I actually only meant to keep track of this for now for post-LTS since I did not want to add any additional issues to the respective milestone but thank a lot for adding it!

[richtja]

solved in #5846