net/netmon: remove usage of direct callbacks from netmon (#17292)

The callback itself is not removed as it is used in other repos, making
it simpler for those to slowly transition to the eventbus.

Updates #15160

Signed-off-by: Claus Lensbøl <claus@tailscale.com>

net/dns/resolver/forwarder_test.go

@@ -122,7 +122,6 @@ func TestResolversWithDelays(t *testing.T) {
 			}
 		})
 	}
-
 }
 
 func TestGetRCode(t *testing.T) {
@@ -454,6 +453,7 @@ func runTestQuery(tb testing.TB, request []byte, modify func(*forwarder), ports
 
 	var dialer tsdial.Dialer
 	dialer.SetNetMon(netMon)
+	dialer.SetBus(bus)
 
 	fwd := newForwarder(logf, netMon, nil, &dialer, health.NewTracker(bus), nil)
 	if modify != nil {