We're trying to gut 90% of the ipnserver package. A lot will get
deleted, some will move to LocalBackend, and a lot is being moved into
this new ipn/ipnauth package which will be leaf-y and testable.
This is a baby step towards moving some stuff to ipnauth.
Update #6417
Updates tailscale/corp#8051
Change-Id: I28bc2126764f46597d92a2d72565009dc6927ee0
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
