Make UserActionActor use RoutingTableActor instead of using RoutingTableView directly.

This pull request also contains two trivial fixex, and a small refactoring
bf985b2 and 76d9c62 are trivial fixes.
7f8d46f is a refactoring.

7c9dca2 and 6a0edb2 are the main job.
Currently, each UserActionActor has a RoutingTableView, so some UserActionActor has empty RoutingTableView if the UserActionActor is restarted and there is no Update message from RoutingTableWorker.
These patches make UserActionActor use RoutingTableView to ensure UserActionActor always gets a valid routing result.