When running `tailscale web` as a standalone process,
it was necessary to send auth requests to QTS using
localhost to avoid hitting the proxy recursively.
However running `tailscale web` as a process means it is
consuming RAM all the time even when it isn't actively
doing anything.
After switching back to the `tailscale web` CGI mode, we
don't need to specifically use localhost for QNAP auth.
This reverts commit e0cadc5496.
Signed-off-by: Denton Gentry <dgentry@tailscale.com>