Add debug logging about events

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

supervisor.go

@@ -133,6 +133,12 @@ func (s *Supervisor) Start() error {
 		// so that nothing else is scheduled over the top of it.
 		goruntime.LockOSThread()
 		for e := range s.events {
+			logrus.WithFields(logrus.Fields{
+				"type":       e.Type,
+				"timestamp":  e.Timestamp,
+				"id":         e.ID,
+				"bundlePath": e.BundlePath,
+			}).Debug("event received")
 			EventsCounter.Inc(1)
 			h, ok := s.handlers[e.Type]
 			if !ok {