Update docs to use control node instead of controller

[samccann]

Our terminology has gotten a bit out of line in the docs. This issue is to find all occurrences of 'controller' and replace with 'control node'.

This should wait until after #281 merges.

[zukizukizuki]

Hi, can I help with this issue? I would like to make a pull request.

[oraNod]

Hi @zukizukizuki yes, please go ahead. Join us on Matrix if you have any questions or would like to chat: https://matrix.to/#/#docs:ansible.com

Thanks.

[felixfontein]

@zukizukizuki please wait with creating a PR until #281 is merged (hopefully will be done by the end of this month).

[zukizukizuki]

@felixfontein
Yes, I understand.