ipn: make Notify.Prefs be a *ipn.PrefsView

It is currently a `ipn.PrefsView` which means when we do a JSON roundtrip,
we go from an invalid Prefs to a valid one.

This makes it a pointer, which fixes the JSON roundtrip.

This was introduced in 0957bc5af2.

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/fake_test.go

@@ -22,7 +22,8 @@ func (b *FakeBackend) Start(opts Options) error {
 	}
 	nl := NeedsLogin
 	if b.notify != nil {
-		b.notify(Notify{Prefs: opts.Prefs.View()})
+		p := opts.Prefs.View()
+		b.notify(Notify{Prefs: &p})
 		b.notify(Notify{State: &nl})
 	}
 	return nil
@@ -83,7 +84,8 @@ func (b *FakeBackend) SetPrefs(new *Prefs) {
 	}
 
 	if b.notify != nil {
-		b.notify(Notify{Prefs: new.View()})
+		p := new.View()
+		b.notify(Notify{Prefs: &p})
 	}
 	if new.WantRunning && !b.live {
 		b.newState(Starting)