platform: drop track_default argument from nmp_rules_manager_new()

All that setting track-default does, is calling nmp_rules_manager_track_default()
when the rules are first accessed.

That is not right API. Since nmp_rules_manager_track_default() is already public
API (good), every caller that wishes this behavior should track these routes explicitly.

src/nm-netns.c

@@ -126,7 +126,11 @@ constructed (GObject *object)
 
 	priv->platform_netns = nm_platform_netns_get (priv->platform);
 
-	priv->rules_manager = nmp_rules_manager_new (priv->platform, TRUE);
+	priv->rules_manager = nmp_rules_manager_new (priv->platform);
+	nmp_rules_manager_track_default (priv->rules_manager,
+	                                 AF_UNSPEC,
+	                                 0,
+	                                 nm_netns_parent_class /* static dummy user-tag */);
 
 	G_OBJECT_CLASS (nm_netns_parent_class)->constructed (object);
 }