SSH was disabled in #10538
Exit node was disabled in #13726
This enables ssh and exit-node options in case of Home Assistant.
Fixes#15552
Signed-off-by: Laszlo Magyar <lmagyar1973@gmail.com>
Adds logic to `checkExitNodePrefsLocked` to return an error when
attempting to use exit nodes on a platform where this is not supported.
This mirrors logic that was added to error out when trying to use `ssh`
on an unsupported platform, and has very similar semantics.
Fixes https://github.com/tailscale/tailscale/issues/13724
Signed-off-by: Mario Minardi <mario@tailscale.com>
