Remove LoginFlags from Backend options.

- It was only used in one currently-unused client.
- It's an imperative command, not a configuration setting.
- The LoginFlags stuff in controlclient feels like it needs
  a refactor anyway.

I'll put this logic back once ipnd owns its state and Backend
commands reflect that.

Signed-Off-By: David Anderson <dave@natulte.net>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f