implemented stopper pattern

-made defer adjustments inline and deleted the separate function.
-adjusted method in upload to take the only parameter it requires.
-Implemented stopper param for reflector server
-Aligned Cluster New to NewCluster
-Adjusted DHT to use StopAndWait
-Removed blocking waitgroup add
-Unified all components under prism.
-Moved defer done outside of functions.
-renamed NewCluster to New
-fixed travis errors.

dht/dht.go

@@ -135,6 +135,11 @@ func (dht *DHT) join() {
 
 	// now call iterativeFind on yourself
 	nf := newContactFinder(dht.node, dht.node.id, false)
+	// stop if dht is stopped
+	go func(finder *contactFinder) {
+		<-dht.stop.Ch()
+		nf.Cancel()
+	}(nf)
 	_, err := nf.Find()
 	if err != nil {
 		log.Errorf("[%s] join: %s", dht.node.id.HexShort(), err.Error())
@@ -151,14 +156,20 @@ func (dht *DHT) Start() error {
 		return errors.Err(err)
 	}
 	conn := listener.(*net.UDPConn)
-
 	err = dht.node.Connect(conn)
 	if err != nil {
 		return err
 	}
-
+	dht.stop.Add(1)
+	go func() {
+		defer dht.stop.Done()
 		dht.join()
+	}()
+	dht.stop.Add(1)
+	go func() {
+		defer dht.stop.Done()
 		dht.startReannouncer()
+	}()
 
 	log.Debugf("[%s] DHT ready on %s (%d nodes found during join)", dht.node.id.HexShort(), dht.contact.Addr().String(), dht.node.rt.Count())
 	return nil
@@ -175,8 +186,7 @@ func (dht *DHT) WaitUntilJoined() {
 // Shutdown shuts down the dht
 func (dht *DHT) Shutdown() {
 	log.Debugf("[%s] DHT shutting down", dht.node.id.HexShort())
-	dht.stop.Stop()
-	dht.stop.Wait()
+	dht.stop.StopAndWait()
 	dht.node.Shutdown()
 	log.Debugf("[%s] DHT stopped", dht.node.id.HexShort())
 }
@@ -245,8 +255,6 @@ func (dht *DHT) Announce(hash Bitmap) error {
 }
 
 func (dht *DHT) startReannouncer() {
-	dht.stop.Add(1)
-	defer dht.stop.Done()
 	tick := time.NewTicker(tReannounce)
 	for {
 		select {
@@ -255,7 +263,9 @@ func (dht *DHT) startReannouncer() {
 		case <-tick.C:
 			dht.lock.RLock()
 			for h := range dht.announced {
+				dht.stop.Add(1)
 				go func(bm Bitmap) {
+					defer dht.stop.Done()
 					if err := dht.Announce(bm); err != nil {
 						log.Error("error re-announcing bitmap - ", err)
 					}