engine: resources: svc: Add symmetric closing

This improves some of the closing in the svc resource. This still needs
lots of improvements, and it's sort of terrible because it was some very
early code written.

engine/resources/svc.go

@@ -69,7 +69,6 @@ func (obj *SvcRes) Validate() error {
 // Init runs some startup code for this resource.
 func (obj *SvcRes) Init(init *engine.Init) error {
 	obj.init = init // save for later
-
 	return nil
 }
 
@@ -108,12 +107,15 @@ func (obj *SvcRes) Watch() error {
 	if err != nil {
 		return errwrap.Wrapf(err, "failed to connect to bus")
 	}
+	defer bus.Close()
 
 	// XXX: will this detect new units?
 	bus.BusObject().Call("org.freedesktop.DBus.AddMatch", 0,
 		"type='signal',interface='org.freedesktop.systemd1.Manager',member='Reloading'")
 	buschan := make(chan *dbus.Signal, 10)
+	defer close(buschan) // NOTE: closing a chan that contains a value is ok
 	bus.Signal(buschan)
+	defer bus.RemoveSignal(buschan) // not needed here, but nice for symmetry
 
 	// notify engine that we're running
 	if err := obj.init.Running(); err != nil {
@@ -124,8 +126,12 @@ func (obj *SvcRes) Watch() error {
 	var send = false                                // send event?
 	var invalid = false                             // does the svc exist or not?
 	var previous bool                               // previous invalid value
-	set := conn.NewSubscriptionSet()                // no error should be returned
+
+	// TODO: do we first need to call conn.Subscribe() ?
+	set := conn.NewSubscriptionSet() // no error should be returned
 	subChannel, subErrors := set.Subscribe()
+	//defer close(subChannel) // cannot close receive-only channel
+	//defer close(subErrors) // cannot close receive-only channel
 	var activeSet = false
 
 	for {