The CLI "up" command is a historical mess, both on the CLI side and
the LocalBackend side. We're getting closer to cleaning it up, but in
the meantime it was again implicated in flaky tests.
In this case, the background goroutine running WatchIPNBus was very
occasionally running enough to get to its StartLoginInteractive call
before the original goroutine did its Start call. That meant
integration tests were very rarely but sometimes logging in with the
default control plane URL out on the internet
(controlplane.tailscale.com) instead of the localhost control server
for tests.
This also might've affected new Headscale etc users on initial "up".
Fixes#11960Fixes#11962
Change-Id: I36f8817b69267a99271b5ee78cb7dbf0fcc0bd34
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>