router: move self node out of config

We are going to use the config struct to allow getting and setting
of the mission control config in the commits that follow. Self node
is not something we want to change, so we move it out for better
separation.

routing/payment_session_test.go

@@ -33,7 +33,7 @@ func TestRequestRoute(t *testing.T) {
 		func() (routingGraph, func(), error) {
 			return &sessionGraph{}, func() {}, nil
 		},
-		&MissionControl{cfg: &MissionControlConfig{}},
+		&MissionControl{},
 		PathFindingConfig{},
 	)
 	if err != nil {