cmd/tailscale: warn if node is locked out on bringup

Updates https://github.com/tailscale/corp/issues/12718
Signed-off-by: Tom DNetto <tom@tailscale.com>
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