Give bind its own wait group

In a waitgroup, all waits must come after all adds

device.go

@@ -35,6 +35,8 @@ type Device struct {
 	}
 
 	net struct {
+		starting sync.WaitGroup
+		stopping sync.WaitGroup
 		mutex  sync.RWMutex
 		bind   Bind   // bind interface
 		port   uint16 // listening port