`routeAdvertiser` is the `iplocal.LocalBackend`. Calls to
`Advertise/UnadvertiseRoute` end up calling `EditPrefs` which in turn
calls `authReconfig` which finally calls `readvertiseAppConnectorRoutes`
which calls `AppConnector.DomainRoutes` and gets stuck on a mutex that
was already held when `routeAdvertiser` was called.
Make all calls to `routeAdvertiser` in `app.AppConnector` go through the
execqueue instead as a short-term fix.
Updates tailscale/corp#25965
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
Co-authored-by: Irbe Krumina <irbe@tailscale.com>
ec5f04b274