health, all: remove health.Global, finish plumbing health.Tracker

Updates #11874
Updates #4136

Change-Id: I414470f71d90be9889d44c3afd53956d9f26cd61
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/dns/resolved.go

@@ -63,13 +63,14 @@ type resolvedManager struct {
 	ctx    context.Context
 	cancel func() // terminate the context, for close
 
-	logf  logger.Logf
-	ifidx int
+	logf   logger.Logf
+	health *health.Tracker
+	ifidx  int
 
 	configCR chan changeRequest // tracks OSConfigs changes and error responses
 }
 
-func newResolvedManager(logf logger.Logf, interfaceName string) (*resolvedManager, error) {
+func newResolvedManager(logf logger.Logf, health *health.Tracker, interfaceName string) (*resolvedManager, error) {
 	iface, err := net.InterfaceByName(interfaceName)
 	if err != nil {
 		return nil, err
@@ -82,8 +83,9 @@ func newResolvedManager(logf logger.Logf, interfaceName string) (*resolvedManage
 		ctx:    ctx,
 		cancel: cancel,
 
-		logf:  logf,
-		ifidx: iface.Index,
+		logf:   logf,
+		health: health,
+		ifidx:  iface.Index,
 
 		configCR: make(chan changeRequest),
 	}
@@ -163,7 +165,7 @@ func (m *resolvedManager) run(ctx context.Context) {
 
 		// Reset backoff and SetNSOSHealth after successful on reconnect.
 		bo.BackOff(ctx, nil)
-		health.Global.SetDNSOSHealth(nil)
+		m.health.SetDNSOSHealth(nil)
 		return nil
 	}
 
@@ -241,7 +243,7 @@ func (m *resolvedManager) run(ctx context.Context) {
 			// Set health while holding the lock, because this will
 			// graciously serialize the resync's health outcome with a
 			// concurrent SetDNS call.
-			health.Global.SetDNSOSHealth(err)
+			m.health.SetDNSOSHealth(err)
 			if err != nil {
 				m.logf("failed to configure systemd-resolved: %v", err)
 			}