Fix sync not returning on room join (#195)

* Use BuildEvent method on room join

* Fix building the list of room members in the sync notifier

* Fix building the list of room members in the sync notifier

* Rephrase comment

src/github.com/matrix-org/dendrite/syncapi/sync/notifier.go

@@ -79,6 +79,9 @@ func (n *Notifier) OnNewEvent(ev *gomatrixserverlib.Event, userID string, pos ty
 				case "invite":
 					userIDs = append(userIDs, userID)
 				case "join":
+					// Manually append the new user's ID so they get notified
+					// along all members in the room
+					userIDs = append(userIDs, userID)
 					n.addJoinedUser(ev.RoomID(), userID)
 				case "leave":
 					fallthrough