When updating via c2n, `tailscale.exe update` runs from `tailscaled.exe`
which runs as SYSTEM. The MSI installer does not start the GUI when
running as SYSTEM. This results in Tailscale just existing on
auto-update, which is ungood.
Instead, always ask the MSI installer to not launch the GUI (via
`TS_NOLAUNCH` argument) and launch it manually with a token from the
current logged in user. The token code was borrowed from
d9081d6ba2/net/dns/wsl_windows.go (L207-L232)
Also, make some logging changes so that these issues are easier to debug
in the future.
Updates #755
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
Extract the self-update logic from cmd/tailscale/cli into a standalone
package that could be used from tailscaled later.
Updates #6995
Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
