ipn: fix netmap change tracking and dns map generation (#609)

Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>

control/controlclient/direct_clone.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by tailscale.com/cmd/cloner -type Persist; DO NOT EDIT.
+
+package controlclient
+
+import ()
+
+// Clone makes a deep copy of Persist.
+// The result aliases no memory with the original.
+func (src *Persist) Clone() *Persist {
+	if src == nil {
+		return nil
+	}
+	dst := new(Persist)
+	*dst = *src
+	return dst
+}