network/route: introduce route_remove_and_cancel()

network/route: introduce route_remove_and_cancel()

Then, replace route_remove_and_drop() with it.

If a route is requested, and the request is already called,
we may not received its reply and notification from the kernel, and
the corresponding Route object may not be remembered. Even in such
case, we need to remove the route, otherwise the route will come
later after the function called.

This is the version for route of f22b586a215962416bdbd692aabb89b1ac2999d0.