net/dns, cmd/tailscaled: plumb system health tracker into dns cleanup (#12969)

fixes tailscale#12968

The dns manager cleanup func was getting passed a nil
health tracker, which will panic.  Fixed to pass it
the system health tracker.

Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -394,7 +394,7 @@ func run() (err error) {
 	// Always clean up, even if we're going to run the server. This covers cases
 	// such as when a system was rebooted without shutting down, or tailscaled
 	// crashed, and would for example restore system DNS configuration.
-	dns.CleanUp(logf, netMon, args.tunname)
+	dns.CleanUp(logf, netMon, sys.HealthTracker(), args.tunname)
 	router.CleanUp(logf, netMon, args.tunname)
 	// If the cleanUp flag was passed, then exit.
 	if args.cleanUp {

net/dns/manager.go

@@ -538,7 +538,9 @@ func (m *Manager) FlushCaches() error {
 // CleanUp restores the system DNS configuration to its original state
 // in case the Tailscale daemon terminated without closing the router.
 // No other state needs to be instantiated before this runs.
-func CleanUp(logf logger.Logf, netMon *netmon.Monitor, interfaceName string) {
+//
+// health must not be nil
+func CleanUp(logf logger.Logf, netMon *netmon.Monitor, health *health.Tracker, interfaceName string) {
 	oscfg, err := NewOSConfigurator(logf, nil, nil, interfaceName)
 	if err != nil {
 		logf("creating dns cleanup: %v", err)
@@ -546,7 +548,7 @@ func CleanUp(logf logger.Logf, netMon *netmon.Monitor, interfaceName string) {
 	}
 	d := &tsdial.Dialer{Logf: logf}
 	d.SetNetMon(netMon)
-	dns := NewManager(logf, oscfg, nil, d, nil, nil, runtime.GOOS)
+	dns := NewManager(logf, oscfg, health, d, nil, nil, runtime.GOOS)
 	if err := dns.Down(); err != nil {
 		logf("dns down: %v", err)
 	}