Do not use log field names 'level', 'msg' or 'time'

By default logrus uses these keys. If we also define one, logrus detects this
and then works around by adding 'fields.whatever' as the key name. However,
in the process of adding the key to the `Fields` it causes a race condition
which can crash the process with concurrent map r/w errors.

src/github.com/matrix-org/go-neb/services/github/github_webhook.go

@@ -107,7 +107,7 @@ func (s *WebhookService) OnReceiveWebhook(w http.ResponseWriter, req *http.Reque
 			}
 			if notifyRoom {
 				logger.WithFields(log.Fields{
-					"msg":     msg,
+					"message":     msg,
 					"room_id": roomID,
 				}).Print("Sending notification to room")
 				if _, e := cli.SendMessageEvent(roomID, "m.room.message", msg); e != nil {

src/github.com/matrix-org/go-neb/services/travisci/travisci.go

@@ -228,7 +228,7 @@ func (s *Service) OnReceiveWebhook(w http.ResponseWriter, req *http.Request, cli
 			}
 
 			logger.WithFields(log.Fields{
-				"msg":     msg,
+				"message":     msg,
 				"room_id": roomID,
 			}).Print("Sending Travis-CI notification to room")
 			if _, e := cli.SendMessageEvent(roomID, "m.room.message", msg); e != nil {