To force an EngineStatus update to the IPN bus.
This is a temporary measure while migrating the Windows GUI entirely
to the LocalAPI and off the old IPN protocol. The old IPN protocol
had RequestEngineStatus and LocalAPI didn't.
Updates #6417
Change-Id: I8ff525fc3dd82bdd9d92c2bdad6db5b75609eacd
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>