cmd/tailscale/cli: move JetKVM scripts to /userdata/init.d for persistence (#17610)

Updates #16524
Updates jetkvm/rv1106-system#34

Signed-off-by: srwareham <ebriouscoding@gmail.com>
(cherry picked from commit f4e2720821)

cmd/tailscale/cli/configure-jetkvm.go

@@ -48,9 +48,12 @@ func runConfigureJetKVM(ctx context.Context, args []string) error {
 	if runtime.GOOS != "linux" || distro.Get() != distro.JetKVM {
 		return errors.New("only implemented on JetKVM")
 	}
-	err := os.WriteFile("/etc/init.d/S22tailscale", bytes.TrimLeft([]byte(`
+	if err := os.MkdirAll("/userdata/init.d", 0755); err != nil {
+		return errors.New("unable to create /userdata/init.d")
+	}
+	err := os.WriteFile("/userdata/init.d/S22tailscale", bytes.TrimLeft([]byte(`
 #!/bin/sh
-# /etc/init.d/S22tailscale
+# /userdata/init.d/S22tailscale
 # Start/stop tailscaled
 
 case "$1" in